如何在Java中打破/退出不同级别的方法调用

Question

比方说我有:

public void one() {
  two();
  // continue here
}
public void two() {
  three();
}
public void three() {
  // exits two() and three() and continues back in one()
}

有没有办法做到这一点？

Answer 1

没有更改方法two()的唯一方法是抛出异常.

如果你可以改变代码,你可以返回一个布尔值,告诉调用者返回.

然而,最简单的解决方案是将方法内联到一个更大的方法中.如果这个太大,你应该以另一种方式重新构建它,而不是在这样的方法之间放置复杂的控件.

说你有

public void one() {
    System.out.println("Start of one.");
    two();
// do something
    System.out.println("End of one.");
}

public void two() {
    System.out.println("Start of two.");
    three();
// do something
    System.out.println("End of two.");
}

public void three() {
    System.out.println("Start of three.");
// do something
    System.out.println("End of three.");
}

如果无法更改two(),则可以添加未经检查的异常;

public void one() {
    System.out.println("Start of one.");
    try {
        two();
    } catch (CancellationException expected) {
    }
// do something
    System.out.println("End of one.");
}

public void two() {
    System.out.println("Start of two.");
    three();
// do something
    System.out.println("End of two.");
}

public void three() {
    System.out.println("Start of three.");
// do something
    System.out.println("End of three.");
    throw new CancellationException(); // use your own exception if possible.
}

你可以返回一个布尔值来表示返回,如果你可以改变两个()

public void one() {
    System.out.println("Start of one.");
    two();
// do something
    System.out.println("End of one.");
}

public void two() {
    System.out.println("Start of two.");
    if (three()) return;
// do something
    System.out.println("End of two.");
}

public boolean three() {
    System.out.println("Start of three.");
// do something
    System.out.println("End of three.");
    return true;
}

或者你可以内联结构

public void one() {
    System.out.println("Start of one.");
    two();
// do something
    System.out.println("End of one.");
}

public void two() {
    System.out.println("Start of two.");
    System.out.println("Start of three.");
// do something for three
    System.out.println("End of three.");
    boolean condition = true;
    if (!condition) {
// do something for two
        System.out.println("End of two.");
    }
}