在java的for循环之外打印我的值 [英] Print the value of i outside the for loop in java

问题描述

我试图打印/获取循环变量i的值，并在for循环之外的另一个方法中使用它。如何做到这一点？

  public void mousePressed（）{
 for（int i = 0; i< 1000; i ++）{
 boxes [i] .openIt（）; 
 
 
 $ / code $ / pre 
 
解决方案
变量在中为语句声明只在中为组件和下面的代码块，见 JLS section 14.14.1.1 ，in （ForInit; Expression; ForUpdate）语句
   
 
 
  $ p 
 
lockquote 
如果ForInit代码是一个局部变量声明，它将作为
执行，如果它是一个局部变量声明语句（§14.4 ）出现在
a块中。
 
如果你希望在之外有 code>，你必须在你想要访问的位置激活的范围内声明它;例如就在之外循环： 
 
 
  int i; 
 for（i = 0; i <1000; ++ i）
; 
 //我可以在这个范围内访问
 System.out.println（i）; 
  
另外，如果更合适，可以声明一个单独的变量并存储感兴趣的值它：
  int k = ...; 
 for（int i = 0; i <1000; ++ i）
 if（condition）//例如
 k = i; 
 // k在这个范围内是可以访问的，我不是
 System.out.println（k）; 
  
有关简要概述，请参阅这个页面，特别是最后的 Loop Scope 例子，它有一个和你的问题完全一样的例子。 / p> 
I am trying to print/get the value of loop variable i and use it in another method outside the for loop. How do I do that?
public void mousePressed() {  
    for (int i = 0; i < 1000; i++){
      boxes[i].openIt();
    }
}

解决方案
Variables declared in the for statement are in scope only in the for components and the following code block, see JLS section 14.14.1.1, in particular:
for ( ForInit ; Expression ; ForUpdate ) Statement



  
If the ForInit code is a local variable declaration, it is executed as
  if it were a local variable declaration statement (§14.4) appearing in
  a block.
If you want to have it available outside the for, you have to declare it in a scope that is active in the location you want to access it; e.g. just outside the for loop:
int i;
for (i = 0; i < 1000; ++ i)
    ;
// i is accessible in this scope
System.out.println(i);
Alternatively, if it is more appropriate, you could declare a separate variable and store the value of interest in it:
int k = ...;
for (int i = 0; i < 1000; ++ i)
    if (condition) // for example
        k = i;
// k is accessible in this scope, i is not
System.out.println(k);
For a brief summary see this page, specifically the Loop Scope example at the end, which has an example that is exactly like your question.


                        
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