如何将此 for 循环转换为 while 循环? [英] How do I convert this for loop into a while loop?

问题描述

我正在创建一个数组程序.我正在练习如何将 for 循环转换为 while 循环，但我无法理解这个概念.

I am creating an array program. I am practicing how to convert for loops to while loops, but I cannot grasp the concept.

如果我有 for 循环:

int [] list = new int [5];

for (int i = 0; i < 5; i++) {
    list [i] = i + 2;
}

如何使它成为 while 循环?

How would I make it a while loop?

这是我的尝试

int [] list = new int [5];
int i = 0;

while (i<5) {
    list [i] = i + 2;
    i++;
}
System.out.print(list[i] + " ");

这是我认为应该做的，但它在我的计算机中出现错误.

This is what I think should be done, but it comes up as an error in my computer.

线程main"中的异常 java.lang.ArrayIndexOutOfBoundsException: 5 at Arrays2.main(Arrays2.java:21)

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 5 at Arrays2.main(Arrays2.java:21)

这是第 21 行

System.out.print(list[i] + " ");

推荐答案

基本for语句的一般结构是:

The general structure of a basic for statement is:

for ( ForInit ; Expression ; ForUpdate ) Statement

• ForInit 是初始值设定项.它首先运行以设置变量等.
• Expression 是一个布尔条件，用于检查是否应该运行 Statement
• Statement 是 Expression 为真时要运行的代码块
• ForUpdate 在 Statement 之后运行，例如根据需要更新变量
• ForInit is the initializer. It is run first to set up variables etc.
• Expression is a boolean condition to check to see if Statement should be run
• Statement is the block of code to be run if Expression is true
• ForUpdate is run after the Statement to e.g. update variables as necessary

ForUpdate 运行后，再次评估 Expression.如果仍然为真，则再次执行Statement，然后ForUpdate；重复此操作，直到 Expression 为 false.

After ForUpdate has been run, Expression is evaluated again. If it is still true, Statement is executed again, then ForUpdate; repeat this until Expression is false.

您可以将其重构为 while 循环，如下所示:

You can restructure this as a while loop as follows:

ForInit;
while (Expression) {
  Statement;
  ForUpdate;
}

为了将此模式应用于真正的"for 循环，只需按照上述方法替换您的块.

In order to apply this pattern to a "real" for loop, just substitute your blocks as described above.

对于上面的示例:

• ForInit => int i = 0
• 表达式 => i <5
• ForUpdate => i++
• 语句 => list [i] = i + 2;
• ForInit => int i = 0
• Expression => i < 5
• ForUpdate => i++
• Statement => list [i] = i + 2;

组合起来:

int i = 0;
while (i < 5) {
  list[i] = i + 2;
  i++;
}

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