【发布时间】：2013-09-01 23:31:09
【问题描述】：
我是 Java 编程新手。这是家庭作业问题的一部分。我需要在数组上提供一组比较方法。我尽力了，这是我迄今为止的尝试。有人可以启发我吗？任何帮助将不胜感激！
我需要遵循的几个要求：
- 不得向 Selector 类添加任何公共方法。您可以随意添加任何您认为合适的私有方法，但不能添加任何公共方法。
- 您不得向 Selector 类添加任何公共或私有字段。
- 您不能导入除 java.util.Arrays 以外的任何内容，但您根本不需要导入它。
- 您只能在最近和最远的解决方案中使用排序 方法。
- 不得修改现有构造函数或添加其他构造函数。此类被设计为严格提供静态方法，不应实例化。
import java.util.Arrays;
/**
* A class that contains various selection methods on arrays.
* All methods assume that the array is completely filled with
* non-null values. If this is not true, the behavior is not specified.
* All the methods throw an IllegalArgumentException if the array
* parameter is null or has zero length. The array parameter to
* each method is guaranteed to not be changed as a result of the call.
*/
public final class Comparision{
/**
* C A N N O T I N S T A N T I A T E T H I S C L A S S .
*
*/
private Comparision(){
}
/**
* Return the element of a nearest to val. This method throws an
* IllegalArgumentException if a is null or has zero-length.
* The array a is not changed as a result of calling this method.
*
* @param a the array to be searched
* @param val the reference value
* @return the element a[i] such that ABS(a[i] - val) is minimum
*
*/
public static int nearest(int[] a, int val) {
int[] a = new int[10];
if (a == null || a.length == 0){
throw new IllegalArgumentException("a is null or has zero-length");
}
int idx = 0;
int distance = Math.abs(a[0]-val);
for(int c = 1; c< a.length; c++){
int cdistance = Math.abs(a[c] - val);
if(cdistance < distance){
idx=c;
distance = cdistance;
}
}
int theNumber = a[idx];
return theNumber;
}
/**
* Return the element of a farthest from val. This method throws an
* IllegalArgumentException if a is null or has zero-length.
* The array a is not changed as a result of calling this method.
*
* @param a the array to be searched
* @param val the reference value
* @return the element a[i] such that ABS(a[i] - val) is maximum
*
*/
public static int farthest(int[] a, int val) {
int[] a = new int[10];
if (a == null || a.length == 0){
throw new IllegalArgumentException("a is null or has zero-length");
}
int idx = 0;
int distance = Math.abs(a[0]-val);
for(int c = 1; c< a.length; c++){
int cdistance = Math.abs(a[c] - val);
if(cdistance > distance){
idx=c;
distance = cdistance;
}
}
int theNumber = a[idx];
return theNumber;
}
/**
* Return the k elements of a nearest to val.
* The array a is not changed as a result of calling this method.
* This method throws an IllegalArgumentException if k is negative.
* This method returns an array of zero length if k == 0 or if
* k > a.length.
*
* @param a the array to be searched
* @param val the reference value
* @param k the number of near elements to identify
* @return the k elements a[i] such that ABS(a[i] - val)
* are the k smallest evaluations
*
*/
public static int[] nearestK(int[] a, int val, int k) {
int[] b = new int[10];
for (int i = 0; i < b.length; i++){
b[i] = Math.abs(a[i] - val);
}
Arrays.sort(b);
int[] c = new int[w];
w = 0;
for (int i = 0; i < k; i++){
if (k < 0){
throw new IllegalArgumentException("k is not invalid!");
}
c[w] = b[i];
w++;
}
return c;
}
/**
* Return the k elements of a farthest from val.
* The array a is not changed as a result of calling this method.
* This method throws an IllegalArgumentException if k is negative.
* This method returns an array of zero length if k == 0 or if
* k > a.length.
*
* @param a the array to be searched
* @param val the reference value
* @param k the number of far elements to identify
* @return the k elements a[i] such that ABS(a[i] - val)
* are the k largest evaluations
*
*/
public static int[] farthestK(int[] a, int val, int k) {
int[] b = new int[10];
for (int i = 0; i < 10; i++){
b[i] = Math.abs(a[i] - val);
}
Arrays.sort(b);
int[] c = new int[w];
int w = 0;
for (int i = array.length-1; i >= array.length-k; i--){
if (k < 0){
throw new IllegalArgumentException("k is not invalid!");
}
else if (k == 0 || k > a.length){
int[] c = "";
}
c[w] = b[i];
w++;
}
return c;
}
/**
* Return the number of elements of a that are greater than val.
*
* @param a the array to be searched
* @param val the reference value
* @return the number of elements a[i] such that a[i] > val
*
*/
public static int numGreater(int[] a, int val) {
int w = 0;
for (int i = 0; i < a.length; i++){
if ((a[i] - val)>0){
w++;
}
return w;
}
/**
* Return an array of all the elements of a that are greater than val.
* If a contains no elements greater than val, this method returns an
* array of zero length.
*
* @param a the array to be searched
* @param val the reference value
* @return the elements a[i] such that a[i] > val
*
*/
public static int[] greater(int[] a, int val){
int[] b = new int[w];
int w = 0;
for (int i = 0; i < a.length; i++){
if ((a[i] - val)>0){
b[w] = a[i];
w++;
}
}
if (w = 0){
int[] b = {};
}
return b;
}
/**
* Return the number of elements of a that are less than val.
*
* @param a the array to be searched
* @param val the reference value
* @return the number of elements a[i] such that a[i] < val
*
*/
public static int numLess(int[] a, int val) {
int w = 0;
for (int i = 0; i < a.length; i++){
if ((a[i] - val)<0){
w++;
}
return w;
}
/**
* Return an array of all the elements of a that are less than val.
* If a contains no elements less than val, this method returns an
* array of zero length.
*
* @param a the array to be searched
* @param val the reference value
* @return the elements a[i] such that a[i] < val
*
*/
public static int[] less(int[] a, int val) {
int[] b = new int[w];
int w = 0;
for (int i = 0; i < a.length; i++){
if ((a[i] - val)<0){
b[w] = a[i];
w++;
}
}
if (w = 0){
int[] b = {};
}
return b;
}
}
【问题讨论】：
-
检查
numGreater的实现。我认为您缺少一些花括号。 -
您确实应该能够解决自己的语法错误。至少我期待它。
-
您使用的是 IDE 吗？蚀？网豆？ IDE 会快速突出显示这些语法错误，以便您轻松发现并修复它们。
-
我正在使用 jGRASP。谢谢！我真的应该在来这里之前摆脱语法错误。