类运行过程的内存分析

Java 虚拟机主要可分为stack、heap、method area三个区域，其中栈主要用来存放基本类型变量，对象引用；堆主要存放类实例；方法区存放静态变量、静态方法、常量池。

1 栈的特点

(1) 栈用来描述方法执行的内存模型。每个方法被调用都会创建一个栈帧(存局部变量、操作数、方法出口)；

(2) JVM 为每个线程创建一个栈，用于存放该线程执行方法的信息(实际参数、局部变量等)；

(3) 栈属于线程私有，不能共享；

(4) 栈的存储特性，FIFO；

(5) 栈是由系统自动分配，速度快；栈是一个连续内存空间；

 

2 堆的特点

(1) 堆用于存储创建好的对象和数组；

(2) JVM 只有一个堆，被所有线程共享；

(3) 堆不是一个连续的内存空间，分配灵活，速度慢；

 

3 方法区

(1) JVM 只有一个方法区，被所有线程共享；

(2) 方法区实际上也是堆，用于存储类、常量相关信息；

(3) 堆用来存放程序中永远不变的内容，如类信息、静态变量、静态方法、字符串常量；

 

4 类运行过程中内存分析

(1) 类实例

package cn.latiny.normal;

/**
 * @author Latiny
 * @version 1.0
 * @description: Human
 * @date 2019/8/2 11:25
 */
public class HumanDemo {

    public static void main(String[] args) throws Exception {
        Street street = new Street();
        street.setName("中华路");
        street.setNumber(10000);
        Location location = new Location("广东", "佛山", street);
        Human human = new Human();
        human.setName("Latiny");
        human.setAge(99);
        human.setLocation(location);
        System.out.println(human);
    }

}

class Humana {

    private String name;
    private int age;
    private Location location;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public Location getLocation() {
        return location;
    }

    public void setLocation(Location location) {
        this.location = location;
    }

    @Override
    public String toString() {
        return "Human{" +
                "name='" + name + '\'' +
                ", age=" + age +
                ", location=" + location +
                '}';
    }
}

class Locationa {

    private String province;
    private String city;
    private Street street;

    public Locationa(String province, String city, Street street){
        this.province = province;
        this.city = city;
        this.street = street;
    }

    public String getProvince() {
        return province;
    }

    public void setProvince(String province) {
        this.province = province;
    }

    public String getCity() {
        return city;
    }

    public void setCity(String city) {
        this.city = city;
    }

    public Street getStreet() {
        return street;
    }

    public void setStreet(Street street) {
        this.street = street;
    }

    @Override
    public String toString() {
        return "Location{" +
                "province='" + province + '\'' +
                ", city='" + city + '\'' +
                ", street=" + street +
                '}';
    }
}

class Streeta  {

    String name;
    int number;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getNumber() {
        return number;
    }

    public void setNumber(int number) {
        this.number = number;
    }

    @Override
    public String toString() {
        return "Street{" +
                "name='" + name + '\'' +
                ", number=" + number +
                '}';
    }
}

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