Java for(int i : x) 有什么作用？
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What does for(int i : x) do?
提问by ksraj98
I am new to Java. I was reading someone's solution to a question and I encountered this:
我是 Java 新手。我正在阅读某人对一个问题的解决方案，我遇到了这个：
int[] ps = new int[N];
for (int i = 0; i < N; i++)
ps[i] = input.nextInt();
int[] counts = new int[1005];
for (int p : ps)
counts[p]++;
What do the last two lines do?
最后两行有什么作用？
采纳答案by user253751
This is a for-each loop. It sets pto the first element of ps, then runs the loop body. Then it sets pto the second element of ps, then runs the loop body. And so on.
这是一个for-each 循环。它设置p为 的第一个元素ps，然后运行循环体。然后它设置p为 的第二个元素ps，然后运行循环体。等等。
It's approximately short for:
它大约是以下内容的缩写：
for(int k = 0; k < ps.length; k++)
{
int p = ps[k];
counts[p]++;
}
回答by Crazyjavahacking
That's a for loop. for (int p : ps)iterates over ints in the psint array
那是一个for循环。for (int p : ps)迭代psint 数组中的整数
回答by silentprogrammer
The line is iterating over each index of array an taking out its value in a sequence in a pvarable.You can check by
该行迭代数组的每个索引，并在变量的序列中取出其值。p您可以通过
for (int p : ps){ // if ps is {1,2,3}
System.out.print(p+" "); // it will print 1 2 3
counts[p]++;
}
回答by Neeraj Jain
For-each loop (Advanced or Enhanced For loop):
For-each 循环（高级或增强型 For 循环）：
The for-each loop introduced in Java5. It is mainly used to traverse array or collection elements. The advantage of for-each loop is that it eliminates the possibility of bugs and makes the code more readable.
Java5 中引入的 for-each 循环。主要用于遍历数组或集合元素。for-each 循环的优点是它消除了错误的可能性并使代码更具可读性。
Syntax
句法
for(data_type variable : array | collection){}
Source :Java For Each Loop
In your case this loop is iterating the Array
在您的情况下，此循环正在迭代 Array
Equivalent Code without For Each Loop
不带 For Each 循环的等效代码
for (int i=0;i<ps.length;i++){
int p=ps[i];
counts[p]++;
}
