易学笔记--从0开始学JAVA（个人纯手工笔记共享 免费！免费！免费！）--第5章 初始化和清理

第5章 初始化和清理/5.2 区分重载方法

 

• 区分重载方法通过参数列表区分重载方法，具体有：

1. 参数数量
2. 参数类型

---

第5章 初始化和清理/5.2 区分重载方法/5.2.1 涉及基本类型的重载

• 重载原则

1. 如果传入的实际基本类型小于方法中声明的形式参数类型，那么实际类型都会被提示
2. 如果传入的实际基本类型大于方法中声明的形式参数类型，那么需要通过类型转换来执行窄化转换

---

第5章 初始化和清理/5.2 区分重载方法/5.2.2 以返回值区分重载方法

• JAVA中不允许以返回值的形式区分重载

---

第5章 初始化和清理/5.3 默认构造器

• 在JAVA中如果没有显式说明构造器，则编译器会默认生成一个无参数的构造器，例如：

---

第5章 初始化和清理/5.4 this关键字

• this关键字：获取对当前对象的引用，只能在方法内部使用，不能在方法外部使用

1. 使用场景
   1. 返回当前对象的引用：
   2. 将自己作为引用传入其它方法：

---

第5章 初始化和清理/5.4 this关键字/5.4.1 在构造器中调用构造器

• this调用构造器：一个方法中只能调用一次，而且位于方法的首行代码，再者this可以调用域和成员方法

1. 源代码：

   //: HelloDate.java
   import java.util.*;
   //import static net.mindview.until.Print.*;
   /** the first Thinking in java example program
     * display a string and today's date
     * @author wengyongsheng 
     * @version 4.0 
   */
   public class HelloDate{
   	/**
   	* @param args array of string arguments
   	*/
     public static void main(String []args) {
     System.out.println("Hello,It's: ");
     System.out.println(new Date());
   //  print("Hello,It's: ");
   }
   }
   
   class Tank{
   	 int level;
   }
   
   class Assignment{
   	public static void main(String []args) {
   		Tank t1 = new Tank();
   		Tank t2 = new Tank();
   		t1.level = 9;
   		t2.level = 47;
   		System.out.println("1:t1.level = " + t1.level + 
   		                   " t2.level = " + t2.level);
       t1 = t2;
       System.out.println("2:t1.level = " + t1.level + 
   		                   " t2.level = " + t2.level);
   		
   		t1.level = 27;
   		System.out.println("3:t1.level = " + t1.level + 
   		                   " t2.level = " + t2.level);                   		                   
   	}
   }
   
   class Letter{
   	 char c;
   }
   
   class PassObject{
   	static void f(Letter y){
   		y.c = 'z';
   	}
   	public static void main(String []args) {
   		Letter x = new Letter();
   		System.out.println("1:x.c= " + x.c);
   		x.c = 'a';
   		System.out.println("2:x.c= " + x.c);
   		f(x);
   		System.out.println("3:x.c= " + x.c);
   	}
   }
   
   class MathOps{
   	public static void main(String []args) {
   		Random rand = new Random(47);
   		int i , j , k;
   		j = rand.nextInt(100) + 1;
   		System.out.println("j = " + j);
   		k = rand.nextInt(100) + 1;
   		System.out.println("k = " + k);
   		i = j + k;
   		System.out.println("i = " + i);
   		
   		float u , v , w;
   		u = rand.nextFloat();
   		System.out.println("u = " + u);
   		v = rand.nextFloat() ;
   		System.out.println("v = " + v);
   		w = u + v;
   		System.out.println("w = " + w);
   	}
   }
   
   class AutoInc{
   	public static void main(String []args) {
   		int i = 1;
   		System.out.println("i = " + i);
   		System.out.println("++i = " + ++i);
   		System.out.println("i++ = " + i++);
   		System.out.println("i2 = " + i);
   		System.out.println("--i = " + --i);
   		System.out.println("i-- = " + i--);
   		System.out.println("i3 = " + i);
    }
   }
   /* output
   i = 1
   ++i = 2
   i++ = 2
   i2=3
   --i = 2
   i-- = 2
   i3=1
   */
   
   class Equaivalence{
   	public static void main(String []args) {
   		Integer n1 = new Integer(47);
   		Integer n2 = new Integer(47);
   		
   		System.out.println(n1 == n2);
   		System.out.println(n1 != n2);
    }
   }
   
   class EqualsMethod{
   	public static void main(String []args) {
   		Integer n1 = new Integer(47);
   		Integer n2 = new Integer(47);
   		
   		System.out.println(n1.equals(n2));
    }
   }
   
   class Value{
   	int i ;
   }
   class EqualsMethod2{
   	public static void main(String []args) {
   		Value v1 = new Value();
   		Value v2 = new Value();
   	 System.out.println(v1.equals(v2));
    }
   }
   
   class ShortCircuit{
   	static boolean test1(int val){
   		System.out.println("test1( " + val + " )");
   		System.out.println("result: "  + (val <1) );
   		return (val < 1);
   	}
   	
   	static boolean test2(int val){
   		System.out.println("test2( " + val + " )");
   		System.out.println("result: "  + (val <1) );
   		return (val < 2);
   	}
   	
   	static boolean test3(int val){
   		System.out.println("test3( " + val + " )");
   		System.out.println("result: "  + (val <1) );
   		return (val < 3);
   	}
   	
   	
   	public static void main(String []args) {
   		
   		boolean b = test1(0) && test2(2) && test2(3);
   		System.out.println("expression is : "  + b );
   	}
   }
   
   class CommaOperator{
   	public static void main(String []args) {
   		for(int i = 1, j = i + 10; i < 5;i++,j = i*2){
   			System.out.println("i =  "  +  i + " j = "  + j);
   		}
    }
   }
   
   
   class ForEachFloat{
   	public static void main(String []args) {
   		Random rand = new Random(47);
   		float f[] = new float[10];
   		for(int i = 0; i < 10;i++){
   			f[i] = rand.nextFloat();
   		}
   		
   		for(float x:f){
   			System.out.println("x =  " + x);
   		}
   		
   		for(char c:"my name".toCharArray()){
   			System.out.println("c =  " + c);
   		}
    }
   }
   
   class LableedWhile{
   	public static void main(String []args) {
   		int i = 0;
   		outer:
   		while(true){
   			System.out.println("Outer while loop");
   			while(true){
   				i++;
   				System.out.println("i = " + i);
   				if(i == 1){
   					System.out.println("continue");
   					continue;
   				}
   				if(i == 3){
   					System.out.println("continue Outer");
   					continue outer;
   				}
   				if(i == 5){
   					System.out.println("break");
   					break;
   				}
   				if(i == 7){
   					System.out.println("break Outer");
   					break outer;
   				}
   			}
   		}
    }
   }
   
   class VoewlsAndConson{
   	public static void main(String []args) {
   		Random rand = new Random(47);
   		for(int i = 0; i < 100;i++){
   			int c = rand.nextInt(26) + 'a';
   			System.out.println("c = " + c);
   			switch(c){
   				case 'a':
   				case 'b':
   				case 'c': System.out.println("vowel");break;
   				case 'y':
   				case 'w':
   				case 'z':System.out.println("consonant");break;
   				default:System.out.println("xxxx");
   			}
   		}
    }
   }
   
   class Flower{
   	int petalCount = 0;
   	String s = "init value";
   	
   	Flower(int peta){
   		petalCount = peta;
   		System.out.println("Flower(int peta)" );
   	}
   	
   	Flower(String ss){
   		s = ss;
   		System.out.println("Flower(String ss) " );
   	}
   	
   	
   	Flower(String s,int patails){
   		this(patails);
   		this.s = s;
   		System.out.println("Flower(String s,int patails) ");
   	}
   	
   	Flower(){
   		this("xxx",1);
   		System.out.println("Flower() ");
   	}
   	public static void main(String []args) {
   		Flower x = new Flower();
   		
   	}
   }

2. 输出结果：

---

第5章 初始化和清理/5.4 this关键字/5.4.2 static的含义

• static 方法

1. 内部调用时只能调用标识有static域或者static方法
2. 可以直接用类名调用

---

第5章 初始化和清理/5.5 清理：终结处理和垃圾回收

• 垃圾回收站和析构函数

1. 垃圾回收站只针对由new申请的内存
2. 垃圾回收站并不一定会发生
3. 对象并不一定凡在垃圾回收站中
4. 垃圾回收站不等同于析构函数

• finalize函数：JAVA用于提供给程序进行对某些对象的回收，单垃圾回收站发生时，首先会调用finalize；等下一次再发生垃圾回收时，再真正回收内存

---

第5章 初始化和清理/5.5 清理：终结处理和垃圾回收/5.5.1 finalize用途所在

• 其实在JAVA中，所有的对象都是有new创建的，凡事由new创建的对象都由垃圾回收负责回收，但是对于非new创建的内存，比如C或者C++用malloc创建的内存，回收站管理不了，只能在finalize方法中显式调用fress进行回收

---

第5章 初始化和清理/5.5 清理：终结处理和垃圾回收/5.5.2 你必选实施清理

---

第5章 初始化和清理/5.5 清理：终结处理和垃圾回收/5.5.3 终结条件

• finalize调用例子

1. 源代码：

   //: HelloDate.java
   import java.util.*;
   //import static net.mindview.until.Print.*;
   /** the first Thinking in java example program
     * display a string and today's date
     * @author wengyongsheng 
     * @version 4.0 
   */
   public class HelloDate{
   	/**
   	* @param args array of string arguments
   	*/
     public static void main(String []args) {
     System.out.println("Hello,It's: ");
     System.out.println(new Date());
   //  print("Hello,It's: ");
   }
   }
   
   class Tank{
   	 int level;
   }
   
   class Assignment{
   	public static void main(String []args) {
   		Tank t1 = new Tank();
   		Tank t2 = new Tank();
   		t1.level = 9;
   		t2.level = 47;
   		System.out.println("1:t1.level = " + t1.level + 
   		                   " t2.level = " + t2.level);
       t1 = t2;
       System.out.println("2:t1.level = " + t1.level + 
   		                   " t2.level = " + t2.level);
   		
   		t1.level = 27;
   		System.out.println("3:t1.level = " + t1.level + 
   		                   " t2.level = " + t2.level);                   		                   
   	}
   }
   
   class Letter{
   	 char c;
   }
   
   class PassObject{
   	static void f(Letter y){
   		y.c = 'z';
   	}
   	public static void main(String []args) {
   		Letter x = new Letter();
   		System.out.println("1:x.c= " + x.c);
   		x.c = 'a';
   		System.out.println("2:x.c= " + x.c);
   		f(x);
   		System.out.println("3:x.c= " + x.c);
   	}
   }
   
   class MathOps{
   	public static void main(String []args) {
   		Random rand = new Random(47);
   		int i , j , k;
   		j = rand.nextInt(100) + 1;
   		System.out.println("j = " + j);
   		k = rand.nextInt(100) + 1;
   		System.out.println("k = " + k);
   		i = j + k;
   		System.out.println("i = " + i);
   		
   		float u , v , w;
   		u = rand.nextFloat();
   		System.out.println("u = " + u);
   		v = rand.nextFloat() ;
   		System.out.println("v = " + v);
   		w = u + v;
   		System.out.println("w = " + w);
   	}
   }
   
   class AutoInc{
   	public static void main(String []args) {
   		int i = 1;
   		System.out.println("i = " + i);
   		System.out.println("++i = " + ++i);
   		System.out.println("i++ = " + i++);
   		System.out.println("i2 = " + i);
   		System.out.println("--i = " + --i);
   		System.out.println("i-- = " + i--);
   		System.out.println("i3 = " + i);
    }
   }
   /* output
   i = 1
   ++i = 2
   i++ = 2
   i2=3
   --i = 2
   i-- = 2
   i3=1
   */
   
   class Equaivalence{
   	public static void main(String []args) {
   		Integer n1 = new Integer(47);
   		Integer n2 = new Integer(47);
   		
   		System.out.println(n1 == n2);
   		System.out.println(n1 != n2);
    }
   }
   
   class EqualsMethod{
   	public static void main(String []args) {
   		Integer n1 = new Integer(47);
   		Integer n2 = new Integer(47);
   		
   		System.out.println(n1.equals(n2));
    }
   }
   
   class Value{
   	int i ;
   }
   class EqualsMethod2{
   	public static void main(String []args) {
   		Value v1 = new Value();
   		Value v2 = new Value();
   	 System.out.println(v1.equals(v2));
    }
   }
   
   class ShortCircuit{
   	static boolean test1(int val){
   		System.out.println("test1( " + val + " )");
   		System.out.println("result: "  + (val <1) );
   		return (val < 1);
   	}
   	
   	static boolean test2(int val){
   		System.out.println("test2( " + val + " )");
   		System.out.println("result: "  + (val <1) );
   		return (val < 2);
   	}
   	
   	static boolean test3(int val){
   		System.out.println("test3( " + val + " )");
   		System.out.println("result: "  + (val <1) );
   		return (val < 3);
   	}
   	
   	
   	public static void main(String []args) {
   		
   		boolean b = test1(0) && test2(2) && test2(3);
   		System.out.println("expression is : "  + b );
   	}
   }
   
   class CommaOperator{
   	public static void main(String []args) {
   		for(int i = 1, j = i + 10; i < 5;i++,j = i*2){
   			System.out.println("i =  "  +  i + " j = "  + j);
   		}
    }
   }
   
   
   class ForEachFloat{
   	public static void main(String []args) {
   		Random rand = new Random(47);
   		float f[] = new float[10];
   		for(int i = 0; i < 10;i++){
   			f[i] = rand.nextFloat();
   		}
   		
   		for(float x:f){
   			System.out.println("x =  " + x);
   		}
   		
   		for(char c:"my name".toCharArray()){
   			System.out.println("c =  " + c);
   		}
    }
   }
   
   class LableedWhile{
   	public static void main(String []args) {
   		int i = 0;
   		outer:
   		while(true){
   			System.out.println("Outer while loop");
   			while(true){
   				i++;
   				System.out.println("i = " + i);
   				if(i == 1){
   					System.out.println("continue");
   					continue;
   				}
   				if(i == 3){
   					System.out.println("continue Outer");
   					continue outer;
   				}
   				if(i == 5){
   					System.out.println("break");
   					break;
   				}
   				if(i == 7){
   					System.out.println("break Outer");
   					break outer;
   				}
   			}
   		}
    }
   }
   
   class VoewlsAndConson{
   	public static void main(String []args) {
   		Random rand = new Random(47);
   		for(int i = 0; i < 100;i++){
   			int c = rand.nextInt(26) + 'a';
   			System.out.println("c = " + c);
   			switch(c){
   				case 'a':
   				case 'b':
   				case 'c': System.out.println("vowel");break;
   				case 'y':
   				case 'w':
   				case 'z':System.out.println("consonant");break;
   				default:System.out.println("xxxx");
   			}
   		}
    }
   }
   
   class Flower{
   	int petalCount = 0;
   	String s = "init value";
   	
   	Flower(int peta){
   		petalCount = peta;
   		System.out.println("Flower(int peta)" );
   	}
   	
   	Flower(String ss){
   		s = ss;
   		System.out.println("Flower(String ss) " );
   	}
   	
   	
   	Flower(String s,int patails){
   		this(patails);
   		this.s = s;
   		System.out.println("Flower(String s,int patails) ");
   	}
   	
   	Flower(){
   		this("xxx",1);
   		System.out.println("Flower() ");
   	}
   	public static void main(String []args) {
   		Flower x = new Flower();
   		
   	}
   }
   
   
   class Book{
    boolean checkedOut = false;
    Book(boolean checkedOut){
    	this.checkedOut = checkedOut;
    }
    void checkIn(){
    	checkedOut = false;
    }
    protected void finalize(){
    	if(checkedOut){
    		System.out.println(" protected void finalize：error ");
    	}
   }
   }
   
   class Tcondition{
   	public static void main(String []args) {
   		Book novel = new Book(true);
   		novel.checkIn();
   		new Book(true);
   		System.gc(); //进行强制终结动作
   	}
   }

2. 输出结果：

---

第5章 初始化和清理/5.5 清理：终结处理和垃圾回收/5.5.4 垃圾回收站如何工作

• 垃圾回收站工作原理

1. 引用计数方法
   1. 原理
      1. 当有引用指向对象时，引用计数加1；当引用离开域时引用计数减去1
      2. 垃圾回收站扫描引用计数列表，当发现引用计数为0时就会马上释放对象空间
   2. 缺点：如果对象存在互相引用，会出现“对象应该被回收，但是引用计数不为0的情况”
   3. 应用：常用来说明垃圾回收站的工作方式，但是实际上不被应用
2. 基于找到“活”的对象：追踪在堆栈或者静态存储区域中的引用

---

第5章 初始化和清理/5.6 成员初始化

• 如果类的数据成员是基本类型，则编译器会默认一个初始值；如果是方法中的局部变量，则必须由程序员进行初始化
• 举例：

---

第5章 初始化和清理/5.6 成员初始化/5.6.1 指定初始化

• 初始化的几种方法

1. 基本类型在定义时直接初始化：
2. 对象类型在定义时直接初始化：
3. 调用方法提供初始值，但是方法必须先有值：
4. 调用方法初始化值，但是方法没有值，这种是不行的：

---

第5章 初始化和清理/5.7 构造器初始化/5.7.1 初始化顺序

• 在构造器初始化之前已经有了默认值：
• 成员数据在任何方法（包括构造器）被调用之前都得到了初始化

1. 举例：

---

第5章 初始化和清理/5.7 构造器初始化/5.7.2 静态数据的初始化

• 静态数据成员先初始化，非静态数据成员后初始化，静态数据成员只初始化一次
• 举例：、
• new对象的时候执行的事情

1. 在堆栈上检查该类是已经存在，如果不存在
   1. 初始化static数据
   2. 初始化非static数据
2. 如果已经存在则直接返回

---

第5章 初始化和清理/5.7 构造器初始化/5.7.3 显式静态初始化

• 静态子句：

1. 在static后面用花括号括起来的对静态成员初始化，
2. 格式：
3. 特点：也是被初始化一次
4. 举例：、

---

第5章 初始化和清理/5.7 构造器初始化/5.7.4 非静态实例初始化

• 实例初始化子句

1. 概念：类似于“静态子句”，也是在对象声明后面进行初始化
2. 格式：
3. 举例：、
4. static声明的对象，如果是在子句中，还是允许再次初始化

   1. class StaticTests{
      
           public  int i = 0;
      
           
      
           public static StaticTest  staticTest1 = new StaticTest(400);
      
           public static StaticTest  staticTest2 = new StaticTest(500);
      
           {
      
                 staticTest1 = new StaticTest(200);
      
                 System.out.println("i="+i);
      
                 
      
                 staticTest2 = new StaticTest(300);
      
                 System.out.println("i="+i);
      
                 
      
           }
      
           
      
           static StaticTest staticTest = new StaticTest(100);
      
           
      
           StaticTests(){
      
                 System.out.println("StaticTests初始化");
      
           }
      
           
      
           StaticTests(int i ){
      
                 this.i = i;
      
                 System.out.println("StaticTests初始化,i=" + i);
      
           }
      
           
      
           public static void main(String[] args) {
      
                 StaticTests staticTest1 = new StaticTests();
      
                 StaticTests staticTest2 = new StaticTests();
      
           }
      
      }

       

   2. StaticTest初始化,i=400

      StaticTest初始化,i=500

      StaticTest初始化,i=100

      StaticTest初始化,i=200

      i=0

      StaticTest初始化,i=300

      i=0

      StaticTests初始化

      StaticTest初始化,i=200

      i=0

      StaticTest初始化,i=300

      i=0

      StaticTests初始化

---

第5章 初始化和清理/5.8 数组初始化

• 数组

1. 概念：指的是数据类型相同的基本类型序列或者对象序列
2. 表示方法：
   1. int a1;：JAVA中采用本方法
   2. int  a1[ ];：C或者C++的写法
3. 数组初始化的方法
   1. 花括号方法：int [ ]a1 = {1,2,3,4,5};
   2. 数组引用：
      1. 格式：int [ ]a2 ; a2 = a1;
      2. 例子：
   3. new后面直接初始化，适应于无固定参数：
      1. Integer [ ]b = new Integer[ ] {new Integer(1),new Integer(2),3};
      2. 举例：
4. 所有的数组（包括基本类型数组）都有一个固定成员：length
5. 数组下标也是从0开始的，最大到length-1
6. 举例：
   1. 源代码：

      //: HelloDate.java
      import java.util.*;
      //import static net.mindview.until.Print.*;
      /** the first Thinking in java example program
        * display a string and today's date
        * @author wengyongsheng 
        * @version 4.0 
      */
      public class HelloDate{
      	/**
      	* @param args array of string arguments
      	*/
        public static void main(String []args) {
        System.out.println("Hello,It's: ");
        System.out.println(new Date());
      //  print("Hello,It's: ");
      }
      }
      
      class Tank{
      	 int level;
      }
      
      class Assignment{
      	public static void main(String []args) {
      		Tank t1 = new Tank();
      		Tank t2 = new Tank();
      		t1.level = 9;
      		t2.level = 47;
      		System.out.println("1:t1.level = " + t1.level + 
      		                   " t2.level = " + t2.level);
          t1 = t2;
          System.out.println("2:t1.level = " + t1.level + 
      		                   " t2.level = " + t2.level);
      		
      		t1.level = 27;
      		System.out.println("3:t1.level = " + t1.level + 
      		                   " t2.level = " + t2.level);                   		                   
      	}
      }
      
      class Letter{
      	 char c;
      }
      
      class PassObject{
      	static void f(Letter y){
      		y.c = 'z';
      	}
      	public static void main(String []args) {
      		Letter x = new Letter();
      		System.out.println("1:x.c= " + x.c);
      		x.c = 'a';
      		System.out.println("2:x.c= " + x.c);
      		f(x);
      		System.out.println("3:x.c= " + x.c);
      	}
      }
      
      class MathOps{
      	public static void main(String []args) {
      		Random rand = new Random(47);
      		int i , j , k;
      		j = rand.nextInt(100) + 1;
      		System.out.println("j = " + j);
      		k = rand.nextInt(100) + 1;
      		System.out.println("k = " + k);
      		i = j + k;
      		System.out.println("i = " + i);
      		
      		float u , v , w;
      		u = rand.nextFloat();
      		System.out.println("u = " + u);
      		v = rand.nextFloat() ;
      		System.out.println("v = " + v);
      		w = u + v;
      		System.out.println("w = " + w);
      	}
      }
      
      class AutoInc{
      	public static void main(String []args) {
      		int i = 1;
      		System.out.println("i = " + i);
      		System.out.println("++i = " + ++i);
      		System.out.println("i++ = " + i++);
      		System.out.println("i2 = " + i);
      		System.out.println("--i = " + --i);
      		System.out.println("i-- = " + i--);
      		System.out.println("i3 = " + i);
       }
      }
      /* output
      i = 1
      ++i = 2
      i++ = 2
      i2=3
      --i = 2
      i-- = 2
      i3=1
      */
      
      class Equaivalence{
      	public static void main(String []args) {
      		Integer n1 = new Integer(47);
      		Integer n2 = new Integer(47);
      		
      		System.out.println(n1 == n2);
      		System.out.println(n1 != n2);
       }
      }
      
      class EqualsMethod{
      	public static void main(String []args) {
      		Integer n1 = new Integer(47);
      		Integer n2 = new Integer(47);
      		
      		System.out.println(n1.equals(n2));
       }
      }
      
      class Value{
      	int i ;
      }
      class EqualsMethod2{
      	public static void main(String []args) {
      		Value v1 = new Value();
      		Value v2 = new Value();
      	 System.out.println(v1.equals(v2));
       }
      }
      
      class ShortCircuit{
      	static boolean test1(int val){
      		System.out.println("test1( " + val + " )");
      		System.out.println("result: "  + (val <1) );
      		return (val < 1);
      	}
      	
      	static boolean test2(int val){
      		System.out.println("test2( " + val + " )");
      		System.out.println("result: "  + (val <1) );
      		return (val < 2);
      	}
      	
      	static boolean test3(int val){
      		System.out.println("test3( " + val + " )");
      		System.out.println("result: "  + (val <1) );
      		return (val < 3);
      	}
      	
      	
      	public static void main(String []args) {
      		
      		boolean b = test1(0) && test2(2) && test2(3);
      		System.out.println("expression is : "  + b );
      	}
      }
      
      class CommaOperator{
      	public static void main(String []args) {
      		for(int i = 1, j = i + 10; i < 5;i++,j = i*2){
      			System.out.println("i =  "  +  i + " j = "  + j);
      		}
       }
      }
      
      
      class ForEachFloat{
      	public static void main(String []args) {
      		Random rand = new Random(47);
      		float f[] = new float[10];
      		for(int i = 0; i < 10;i++){
      			f[i] = rand.nextFloat();
      		}
      		
      		for(float x:f){
      			System.out.println("x =  " + x);
      		}
      		
      		for(char c:"my name".toCharArray()){
      			System.out.println("c =  " + c);
      		}
       }
      }
      
      class LableedWhile{
      	public static void main(String []args) {
      		int i = 0;
      		outer:
      		while(true){
      			System.out.println("Outer while loop");
      			while(true){
      				i++;
      				System.out.println("i = " + i);
      				if(i == 1){
      					System.out.println("continue");
      					continue;
      				}
      				if(i == 3){
      					System.out.println("continue Outer");
      					continue outer;
      				}
      				if(i == 5){
      					System.out.println("break");
      					break;
      				}
      				if(i == 7){
      					System.out.println("break Outer");
      					break outer;
      				}
      			}
      		}
       }
      }
      
      class VoewlsAndConson{
      	public static void main(String []args) {
      		Random rand = new Random(47);
      		for(int i = 0; i < 100;i++){
      			int c = rand.nextInt(26) + 'a';
      			System.out.println("c = " + c);
      			switch(c){
      				case 'a':
      				case 'b':
      				case 'c': System.out.println("vowel");break;
      				case 'y':
      				case 'w':
      				case 'z':System.out.println("consonant");break;
      				default:System.out.println("xxxx");
      			}
      		}
       }
      }
      
      class Flower{
      	int petalCount = 0;
      	String s = "init value";
      	
      	Flower(int peta){
      		petalCount = peta;
      		System.out.println("Flower(int peta)" );
      	}
      	
      	Flower(String ss){
      		s = ss;
      		System.out.println("Flower(String ss) " );
      	}
      	
      	
      	Flower(String s,int patails){
      		this(patails);
      		this.s = s;
      		System.out.println("Flower(String s,int patails) ");
      	}
      	
      	Flower(){
      		this("xxx",1);
      		System.out.println("Flower() ");
      	}
      	public static void main(String []args) {
      		Flower x = new Flower();
      		
      	}
      }
      
      
      class Book{
       boolean checkedOut = false;
       Book(boolean checkedOut){
       	this.checkedOut = checkedOut;
       }
       void checkIn(){
       	checkedOut = false;
       }
       protected void finalize(){
       	if(checkedOut){
       		System.out.println(" protected void finalize：error ");
       	}
      }
      }
      
      class Tcondition{
      	public static void main(String []args) {
      		Book novel = new Book(true);
      		novel.checkIn();
      		new Book(true);
      		System.gc(); //进行强制终结动作
      	}
      }
      
      
      class ArrayClassObj{
      	public static void main(String []args) {
      		Random rand = new Random (46);
      		Integer []a = new Integer[rand.nextInt(20)];
      		System.out.println("a.length = " + a.length);
      		for(int i= 0; i < a.length;i++){
      			a[i] = rand.nextInt(500);
      		}
      		System.out.println(Arrays.toString(a));
      		
      	}
      }

   2. 输出结果：

---

第5章 初始化和清理/5.8 数组初始化/5.8.1 可变参数列表

• 数组方式可变参数列表：举例

1. 源代码：

   //: HelloDate.java
   import java.util.*;
   //import static net.mindview.until.Print.*;
   /** the first Thinking in java example program
     * display a string and today's date
     * @author wengyongsheng 
     * @version 4.0 
   */
   public class HelloDate{
   	/**
   	* @param args array of string arguments
   	*/
     public static void main(String []args) {
     System.out.println("Hello,It's: ");
     System.out.println(new Date());
   //  print("Hello,It's: ");
   }
   }
   
   class Tank{
   	 int level;
   }
   
   class Assignment{
   	public static void main(String []args) {
   		Tank t1 = new Tank();
   		Tank t2 = new Tank();
   		t1.level = 9;
   		t2.level = 47;
   		System.out.println("1:t1.level = " + t1.level + 
   		                   " t2.level = " + t2.level);
       t1 = t2;
       System.out.println("2:t1.level = " + t1.level + 
   		                   " t2.level = " + t2.level);
   		
   		t1.level = 27;
   		System.out.println("3:t1.level = " + t1.level + 
   		                   " t2.level = " + t2.level);                   		                   
   	}
   }
   
   class Letter{
   	 char c;
   }
   
   class PassObject{
   	static void f(Letter y){
   		y.c = 'z';
   	}
   	public static void main(String []args) {
   		Letter x = new Letter();
   		System.out.println("1:x.c= " + x.c);
   		x.c = 'a';
   		System.out.println("2:x.c= " + x.c);
   		f(x);
   		System.out.println("3:x.c= " + x.c);
   	}
   }
   
   class MathOps{
   	public static void main(String []args) {
   		Random rand = new Random(47);
   		int i , j , k;
   		j = rand.nextInt(100) + 1;
   		System.out.println("j = " + j);
   		k = rand.nextInt(100) + 1;
   		System.out.println("k = " + k);
   		i = j + k;
   		System.out.println("i = " + i);
   		
   		float u , v , w;
   		u = rand.nextFloat();
   		System.out.println("u = " + u);
   		v = rand.nextFloat() ;
   		System.out.println("v = " + v);
   		w = u + v;
   		System.out.println("w = " + w);
   	}
   }
   
   class AutoInc{
   	public static void main(String []args) {
   		int i = 1;
   		System.out.println("i = " + i);
   		System.out.println("++i = " + ++i);
   		System.out.println("i++ = " + i++);
   		System.out.println("i2 = " + i);
   		System.out.println("--i = " + --i);
   		System.out.println("i-- = " + i--);
   		System.out.println("i3 = " + i);
    }
   }
   /* output
   i = 1
   ++i = 2
   i++ = 2
   i2=3
   --i = 2
   i-- = 2
   i3=1
   */
   
   class Equaivalence{
   	public static void main(String []args) {
   		Integer n1 = new Integer(47);
   		Integer n2 = new Integer(47);
   		
   		System.out.println(n1 == n2);
   		System.out.println(n1 != n2);
    }
   }
   
   class EqualsMethod{
   	public static void main(String []args) {
   		Integer n1 = new Integer(47);
   		Integer n2 = new Integer(47);
   		
   		System.out.println(n1.equals(n2));
    }
   }
   
   class Value{
   	int i ;
   }
   class EqualsMethod2{
   	public static void main(String []args) {
   		Value v1 = new Value();
   		Value v2 = new Value();
   	 System.out.println(v1.equals(v2));
    }
   }
   
   class ShortCircuit{
   	static boolean test1(int val){
   		System.out.println("test1( " + val + " )");
   		System.out.println("result: "  + (val <1) );
   		return (val < 1);
   	}
   	
   	static boolean test2(int val){
   		System.out.println("test2( " + val + " )");
   		System.out.println("result: "  + (val <1) );
   		return (val < 2);
   	}
   	
   	static boolean test3(int val){
   		System.out.println("test3( " + val + " )");
   		System.out.println("result: "  + (val <1) );
   		return (val < 3);
   	}
   	
   	
   	public static void main(String []args) {
   		
   		boolean b = test1(0) && test2(2) && test2(3);
   		System.out.println("expression is : "  + b );
   	}
   }
   
   class CommaOperator{
   	public static void main(String []args) {
   		for(int i = 1, j = i + 10; i < 5;i++,j = i*2){
   			System.out.println("i =  "  +  i + " j = "  + j);
   		}
    }
   }
   
   
   class ForEachFloat{
   	public static void main(String []args) {
   		Random rand = new Random(47);
   		float f[] = new float[10];
   		for(int i = 0; i < 10;i++){
   			f[i] = rand.nextFloat();
   		}
   		
   		for(float x:f){
   			System.out.println("x =  " + x);
   		}
   		
   		for(char c:"my name".toCharArray()){
   			System.out.println("c =  " + c);
   		}
    }
   }
   
   class LableedWhile{
   	public static void main(String []args) {
   		int i = 0;
   		outer:
   		while(true){
   			System.out.println("Outer while loop");
   			while(true){
   				i++;
   				System.out.println("i = " + i);
   				if(i == 1){
   					System.out.println("continue");
   					continue;
   				}
   				if(i == 3){
   					System.out.println("continue Outer");
   					continue outer;
   				}
   				if(i == 5){
   					System.out.println("break");
   					break;
   				}
   				if(i == 7){
   					System.out.println("break Outer");
   					break outer;
   				}
   			}
   		}
    }
   }
   
   class VoewlsAndConson{
   	public static void main(String []args) {
   		Random rand = new Random(47);
   		for(int i = 0; i < 100;i++){
   			int c = rand.nextInt(26) + 'a';
   			System.out.println("c = " + c);
   			switch(c){
   				case 'a':
   				case 'b':
   				case 'c': System.out.println("vowel");break;
   				case 'y':
   				case 'w':
   				case 'z':System.out.println("consonant");break;
   				default:System.out.println("xxxx");
   			}
   		}
    }
   }
   
   class Flower{
   	int petalCount = 0;
   	String s = "init value";
   	
   	Flower(int peta){
   		petalCount = peta;
   		System.out.println("Flower(int peta)" );
   	}
   	
   	Flower(String ss){
   		s = ss;
   		System.out.println("Flower(String ss) " );
   	}
   	
   	
   	Flower(String s,int patails){
   		this(patails);
   		this.s = s;
   		System.out.println("Flower(String s,int patails) ");
   	}
   	
   	Flower(){
   		this("xxx",1);
   		System.out.println("Flower() ");
   	}
   	public static void main(String []args) {
   		Flower x = new Flower();
   		
   	}
   }
   
   
   class Book{
    boolean checkedOut = false;
    Book(boolean checkedOut){
    	this.checkedOut = checkedOut;
    }
    void checkIn(){
    	checkedOut = false;
    }
    protected void finalize(){
    	if(checkedOut){
    		System.out.println(" protected void finalize：error ");
    	}
   }
   }
   
   class Tcondition{
   	public static void main(String []args) {
   		Book novel = new Book(true);
   		novel.checkIn();
   		new Book(true);
   		System.gc(); //进行强制终结动作
   	}
   }
   
   
   class ArrayClassObj{
   	public static void main(String []args) {
   		Random rand = new Random (46);
   		Integer []a = new Integer[rand.nextInt(20)];
   		System.out.println("a.length = " + a.length);
   		for(int i= 0; i < a.length;i++){
   			a[i] = rand.nextInt(500);
   		}
   		System.out.println(Arrays.toString(a));
   		
   	}
   }
   
   class VarArgs{
   	
   	static void printArray(Object [] args) {
   		for(Object obj : args){
   			System.out.println("obj = " + obj);
   		}
   	}
   	
   	public static void main(String []args) {
   		printArray(new Object[]
   		           {new Integer(10),
   		           	new Integer(20),
   		           	new Integer(30)});
   
       printArray(new Object[]
   		           {"one",
   		           	"two",
   		            "thress"});
   	}
   }

    

2. 结果输出：

• JAVA SE5后新可变参数方法：
• 源代码：

  //: HelloDate.java
  import java.util.*;
  //import static net.mindview.until.Print.*;
  /** the first Thinking in java example program
    * display a string and today's date
    * @author wengyongsheng 
    * @version 4.0 
  */
  public class HelloDate{
  	/**
  	* @param args array of string arguments
  	*/
    public static void main(String []args) {
    System.out.println("Hello,It's: ");
    System.out.println(new Date());
  //  print("Hello,It's: ");
  }
  }
  
  class Tank{
  	 int level;
  }
  
  class Assignment{
  	public static void main(String []args) {
  		Tank t1 = new Tank();
  		Tank t2 = new Tank();
  		t1.level = 9;
  		t2.level = 47;
  		System.out.println("1:t1.level = " + t1.level + 
  		                   " t2.level = " + t2.level);
      t1 = t2;
      System.out.println("2:t1.level = " + t1.level + 
  		                   " t2.level = " + t2.level);
  		
  		t1.level = 27;
  		System.out.println("3:t1.level = " + t1.level + 
  		                   " t2.level = " + t2.level);                   		                   
  	}
  }
  
  class Letter{
  	 char c;
  }
  
  class PassObject{
  	static void f(Letter y){
  		y.c = 'z';
  	}
  	public static void main(String []args) {
  		Letter x = new Letter();
  		System.out.println("1:x.c= " + x.c);
  		x.c = 'a';
  		System.out.println("2:x.c= " + x.c);
  		f(x);
  		System.out.println("3:x.c= " + x.c);
  	}
  }
  
  class MathOps{
  	public static void main(String []args) {
  		Random rand = new Random(47);
  		int i , j , k;
  		j = rand.nextInt(100) + 1;
  		System.out.println("j = " + j);
  		k = rand.nextInt(100) + 1;
  		System.out.println("k = " + k);
  		i = j + k;
  		System.out.println("i = " + i);
  		
  		float u , v , w;
  		u = rand.nextFloat();
  		System.out.println("u = " + u);
  		v = rand.nextFloat() ;
  		System.out.println("v = " + v);
  		w = u + v;
  		System.out.println("w = " + w);
  	}
  }
  
  class AutoInc{
  	public static void main(String []args) {
  		int i = 1;
  		System.out.println("i = " + i);
  		System.out.println("++i = " + ++i);
  		System.out.println("i++ = " + i++);
  		System.out.println("i2 = " + i);
  		System.out.println("--i = " + --i);
  		System.out.println("i-- = " + i--);
  		System.out.println("i3 = " + i);
   }
  }
  /* output
  i = 1
  ++i = 2
  i++ = 2
  i2=3
  --i = 2
  i-- = 2
  i3=1
  */
  
  class Equaivalence{
  	public static void main(String []args) {
  		Integer n1 = new Integer(47);
  		Integer n2 = new Integer(47);
  		
  		System.out.println(n1 == n2);
  		System.out.println(n1 != n2);
   }
  }
  
  class EqualsMethod{
  	public static void main(String []args) {
  		Integer n1 = new Integer(47);
  		Integer n2 = new Integer(47);
  		
  		System.out.println(n1.equals(n2));
   }
  }
  
  class Value{
  	int i ;
  }
  class EqualsMethod2{
  	public static void main(String []args) {
  		Value v1 = new Value();
  		Value v2 = new Value();
  	 System.out.println(v1.equals(v2));
   }
  }
  
  class ShortCircuit{
  	static boolean test1(int val){
  		System.out.println("test1( " + val + " )");
  		System.out.println("result: "  + (val <1) );
  		return (val < 1);
  	}
  	
  	static boolean test2(int val){
  		System.out.println("test2( " + val + " )");
  		System.out.println("result: "  + (val <1) );
  		return (val < 2);
  	}
  	
  	static boolean test3(int val){
  		System.out.println("test3( " + val + " )");
  		System.out.println("result: "  + (val <1) );
  		return (val < 3);
  	}
  	
  	
  	public static void main(String []args) {
  		
  		boolean b = test1(0) && test2(2) && test2(3);
  		System.out.println("expression is : "  + b );
  	}
  }
  
  class CommaOperator{
  	public static void main(String []args) {
  		for(int i = 1, j = i + 10; i < 5;i++,j = i*2){
  			System.out.println("i =  "  +  i + " j = "  + j);
  		}
   }
  }
  
  
  class ForEachFloat{
  	public static void main(String []args) {
  		Random rand = new Random(47);
  		float f[] = new float[10];
  		for(int i = 0; i < 10;i++){
  			f[i] = rand.nextFloat();
  		}
  		
  		for(float x:f){
  			System.out.println("x =  " + x);
  		}
  		
  		for(char c:"my name".toCharArray()){
  			System.out.println("c =  " + c);
  		}
   }
  }
  
  class LableedWhile{
  	public static void main(String []args) {
  		int i = 0;
  		outer:
  		while(true){
  			System.out.println("Outer while loop");
  			while(true){
  				i++;
  				System.out.println("i = " + i);
  				if(i == 1){
  					System.out.println("continue");
  					continue;
  				}
  				if(i == 3){
  					System.out.println("continue Outer");
  					continue outer;
  				}
  				if(i == 5){
  					System.out.println("break");
  					break;
  				}
  				if(i == 7){
  					System.out.println("break Outer");
  					break outer;
  				}
  			}
  		}
   }
  }
  
  class VoewlsAndConson{
  	public static void main(String []args) {
  		Random rand = new Random(47);
  		for(int i = 0; i < 100;i++){
  			int c = rand.nextInt(26) + 'a';
  			System.out.println("c = " + c);
  			switch(c){
  				case 'a':
  				case 'b':
  				case 'c': System.out.println("vowel");break;
  				case 'y':
  				case 'w':
  				case 'z':System.out.println("consonant");break;
  				default:System.out.println("xxxx");
  			}
  		}
   }
  }
  
  class Flower{
  	int petalCount = 0;
  	String s = "init value";
  	
  	Flower(int peta){
  		petalCount = peta;
  		System.out.println("Flower(int peta)" );
  	}
  	
  	Flower(String ss){
  		s = ss;
  		System.out.println("Flower(String ss) " );
  	}
  	
  	
  	Flower(String s,int patails){
  		this(patails);
  		this.s = s;
  		System.out.println("Flower(String s,int patails) ");
  	}
  	
  	Flower(){
  		this("xxx",1);
  		System.out.println("Flower() ");
  	}
  	public static void main(String []args) {
  		Flower x = new Flower();
  		
  	}
  }
  
  
  class Book{
   boolean checkedOut = false;
   Book(boolean checkedOut){
   	this.checkedOut = checkedOut;
   }
   void checkIn(){
   	checkedOut = false;
   }
   protected void finalize(){
   	if(checkedOut){
   		System.out.println(" protected void finalize：error ");
   	}
  }
  }
  
  class Tcondition{
  	public static void main(String []args) {
  		Book novel = new Book(true);
  		novel.checkIn();
  		new Book(true);
  		System.gc(); //进行强制终结动作
  	}
  }
  
  
  class ArrayClassObj{
  	public static void main(String []args) {
  		Random rand = new Random (46);
  		Integer []a = new Integer[rand.nextInt(20)];
  		System.out.println("a.length = " + a.length);
  		for(int i= 0; i < a.length;i++){
  			a[i] = rand.nextInt(500);
  		}
  		System.out.println(Arrays.toString(a));
  		
  	}
  }
  
  class VarArgs{
  	
  	static void printArray(Object [] args) {
  		for(Object obj : args){
  			System.out.println("obj = " + obj);
  		}
  	}
  	
  	public static void main(String []args) {
  		printArray(new Object[]
  		           {new Integer(10),
  		           	new Integer(20),
  		           	new Integer(30)});
  
      printArray(new Object[]
  		           {"one",
  		           	"two",
  		            "thress"});
  	}
  }
  
  class NewVarArgs{
  	
  	static void printArray(Object ... args) {
  		for(Object obj : args){
  			System.out.println("obj = " + obj);
  		}
  	}
  	
  	public static void main(String []args) {
  		printArray(
  		            new Integer(1),
  		           	new Integer(2),
  		           	new Integer(3));
  
      printArray("one1",
  		           	"two2",
  		            "thress3");
  	}
  }

• 结果输出：
• 可变参数的类可以为任何类型，包括基本类型
  1. 比如：String类型
  2. 比如：Int类型：
• 可变参数的重载

1. 可变参数重载举例（参数只有可变参数）：
2. 可变参数重载举例（参数有可变参数和不变参数）：

---

第5章 初始化和清理/5.9 枚举类型

• 枚举类型

1. 关键字：enum
2. 自动添加的方法
   1. toString( )：显示实例名称
   2. ordinal( )：显示声明顺序
   3. values( )：显示常量对应值 
3. 举例：
   1. 源代码：
   2. 输出结果：
4. enum与switch的结合使用：