java - {} 格式不同？格式化困境

Question

这个问题已经有答案了:

Is it ok if I omit curly braces in Java? [closed] (16 个回答)

已关闭 8 年前。

所以我有这个代码并打印它:

import java.util.*;

public class Reverse_Copy {

    public static void main(String[] args){

        //create an array and covert to list
        Character[] ray = {'p','w','n'};
        List<Character> l = new ArrayList<Character>(Arrays.asList(ray));
        System.out.println("List is: ");
        output(l);

        //reverse and print out the list
        Collections.reverse(l);
        System.out.println("After reverse: ");
        output(l);

        //create a new array and a new list
        Character[] newray = new Character[3];
        List<Character> listCopy = new ArrayList<Character>(Arrays.asList(newray));

        //copy contens of list l into list listCopy
        Collections.copy(listCopy, l);
        System.out.println("Copy of list: ");
        output(listCopy);

        //fill collection with crap
        Collections.fill(l,'X');
        System.out.println("After filling the list: ");
        output(l);

    }

    private static void output(List<Character> thelist){

        for(Character thing: thelist)
            System.out.printf("%s ", thing);
            System.out.println();


    }

}

这是打印:

List is: 
p w n 
After reverse: 
n w p 
Copy of list: 
n w p 

这与 enhanced for loops 的括号中的代码相同。 .

    import java.util.*;

    public class Reverse_Copy {

    public static void main(String[] args){

        //create an array and covert to list
        Character[] ray = {'p','w','n'};
        List<Character> l = new ArrayList<Character>(Arrays.asList(ray));
        System.out.println("List is: ");
        output(l);

        //reverse and print out the list
        Collections.reverse(l);
        System.out.println("After reverse: ");
        output(l);

        //create a new array and a new list
        Character[] newray = new Character[3];
        List<Character> listCopy = new ArrayList<Character>(Arrays.asList(newray));

        //copy contens of list l into list listCopy
        Collections.copy(listCopy, l);
        System.out.println("Copy of list: ");
        output(listCopy);

        //fill collection with crap
        Collections.fill(l,'X');
        System.out.println("After filling the list: ");
        output(l);

    }

    private static void output(List<Character> thelist){

        for(Character thing: thelist){
            System.out.printf("%s ", thing);
            System.out.println();
        }

    }

}

这是打印内容:

List is: 
p 
w 
n 
After reverse: 
n 
w 
p 
Copy of list: 
n 
w 
p 
After filling the list: 
X 
X 
X 

我觉得这很奇怪，简单的括号与打印方式有什么关系？对于为什么会发生这种情况有什么想法吗？如果你不相信我，你可以自己测试一下。我找不到发生这种情况的任何理由。非常奇怪。

<小时/>

编辑:重复网站中的答案仅证明它不会改变任何内容。证明添加花括号如何改变事物而不是保持不变。

Answer 1

当您省略 for 循环中的括号时，仅执行第一行:

 for(Character thing: thelist)
        System.out.printf("%s ", thing);
        System.out.println();

它将对 thelist 中的每个元素执行 printf 行，然后仅执行一次 println 。不要让缩进欺骗了你。

还有

 for(Character thing: thelist){
    System.out.printf("%s ", thing);
    System.out.println();
}

它将针对 thelist 中的每个元素执行 printf 行和 println 行。