Java 开关 - 在缺少中断后执行不正确的情况。为什么？

Question

这个问题在这里已经有了答案:





Why do we need break after case statements?

(17 个回答)


6年前关闭。




我在网上学习 Java 并来到了关于 switch 的类(class)。为了鬼混，我在特定情况(将被执行)之后删除了一个中断。我原以为它会检查下一个案例，看看条件是否为假，然后在退出之前跳到默认案例。相反，它执行了错误的案例并在默认案例之前中断。

这里出了什么问题？

public class Switch {
    public static void main(String[] args) {

        char penaltyKick = 'R';

        switch (penaltyKick) {

            case 'L': System.out.println("Messi shoots to the left and scores!");
                                break; 
            case 'R': System.out.println("Messi shoots to the right and misses the goal!");

            case 'C': System.out.println("Messi shoots down the center, but the keeper blocks it!");
                                break;
            default:
                System.out.println("Messi is in position...");

        }

    }
}

编辑:忘了提。输出是:

Messi shoots to the right and misses the goal! 
Messi shoots down the center, but the keeper blocks it!

Answer 1

如果您缺少 break , 执行到下一个 case没有再次检查条件。见 here :

The break statements are necessary because without them, statements in switch blocks fall through: All statements after the matching case label are executed in sequence, regardless of the expression of subsequent case labels, until a break statement is encountered.