用于Java中的每个循环 [英] For-each Loop in Java

问题描述

我有一个示例代码，它创建了一个大小为10的数组，并尝试在For循环中用反向值初始化它，例如：（9,8,7,6,5 ... 0）：

  int [] array = new int [10]; 
 for（int i = array.length  -  1，j = 0; i> = 0; i--，j ++）{
 System.out.println（i =的当前值+ i 
 +当前值j =+ j）; 
 array [j] = i; 
 System.out.println（Array：+ j +=+ i）; 
 
（int k：array）{
 System.out.println（array [k]）; 
} 
  

到目前为止，

  i = 9的当前值j = 0的现值
数组：0 = 9 
 i的当前值8 = j的当前值
数组：1 = 8 
 i的当前值7 = j的当前值
数组：2 = 7 
 i的当前值6 = j的当前值3 
数组：3 = 6 
 i的当前值5 j的当前值= 4 
数组：4 = 5 
当前值i = 4当前值j = 5 
数组：5 = 4 
当前值i = 3当前值= 6 
数组：6 = 3 
 i = 2的当前值j = 7的当前值
数组：7 = 2 
 i的当前值j = 8的当前值
数组：8 = 1 
 i的当前值0 = j的当前值9 
数组：9 = 0 
  

问题在于For-each循环到底是在数组中打印值：

<$对于（int k：array）{
System.out.println（array [k]）; pre>

$ / code $ / pre
$ b $ p

打印数组的值是0,1,2 ... 9应该是9,8,7 ... 0

当我使用常规的For循环打印数组时，它正常工作。我在这里错过了一些有趣的事情吗？基本上，既然（int k：array） code>导致 k 遍历数组中的值，而不是索引，所做的相当于 p>



  System.out.println（array [array [0]]）; 
 System.out.println（array [array [1]]）; 
 System.out.println（array [array [2]]）; 
 System.out.println（array [array [3]]）; 
 ... 
 System.out.println（array [array [9]]）; 
  

这不是您想要的。

I have a sample code which creates an "array" of size 10 and tries to initialize it with reverse values in a For loop e.g:(9,8,7,6,5...0):

int[] array = new int[10];
        for (int i = array.length - 1, j = 0; i >= 0; i--, j++) {
            System.out.println("Present value of i=" + i
                    + " Present value of j=" + j);
            array[j] = i;
            System.out.println("Array:" + j + "=" + i);
        }
        for (int k : array) {
            System.out.println(array[k]);
        }

So far so good. This is the output from console which is perfect:

Present value of i=9 Present value of j=0
Array:0=9
Present value of i=8 Present value of j=1
Array:1=8
Present value of i=7 Present value of j=2
Array:2=7
Present value of i=6 Present value of j=3
Array:3=6
Present value of i=5 Present value of j=4
Array:4=5
Present value of i=4 Present value of j=5
Array:5=4
Present value of i=3 Present value of j=6
Array:6=3
Present value of i=2 Present value of j=7
Array:7=2
Present value of i=1 Present value of j=8
Array:8=1
Present value of i=0 Present value of j=9
Array:9=0

The issue is with For-each loop in the end which is just printing the values in array:

for (int k : array) {
            System.out.println(array[k]);
        }

The values printed array are 0,1,2...9 where it should be 9,8,7...0

When I use the regular For loop to print the array, it works normally. Am I missing some funny business here?

解决方案

Basically, since (int k : array) causes k to go through the values in the array, not the indexes, what you've done is equivalent to

System.out.println(array[array[0]]);
System.out.println(array[array[1]]);
System.out.println(array[array[2]]);
System.out.println(array[array[3]]);
...
System.out.println(array[array[9]]);

which isn't what you want.

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