如何在Java中中斷/退出不同級別的方法調用

Question

比方說我有：

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

有什么方法可以做到這一點？

Answer 1

沒有更改方法two（）的唯一方法是引發Exception。

如果可以更改代碼，則可以返回一個布爾值，告訴調用者返回。

但是，最簡單的解決方案是將這些方法內聯為一個更大的方法。 如果太大，則應以其他方式重新構造它，而不要在這樣的方法之間放置復雜的控件。

---

說你有

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.");
}

---

如果您不能更改two（），則可以添加未檢查的異常；

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.
}

---

如果可以更改two（），則可以返回一個布爾值來表示return。

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;
}

---

或者您可以內聯結構

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.");
    }
}

Answer 2

查看您的代碼，如果調用一個，則調用兩個，然后調用三個。如果保持原樣，這正是它的作用。 在您的一個函數中，第二個之后的行僅在其從兩個返回之后才完成，並且直到兩個以三個結束時才這樣做。

Answer 3

假設您可以更改two()方法，也許您想要這樣的東西？

public void one() {
    two();
    // continue here from condition
}

public void two() {
    if (three()) {
        // go back due to condition 
        return;
    }

    // condition wasn't met
}

public boolean three() {
    // some condition is determined here

    if (condition) {
        // exits two() and three() and continues back in one()
        return true;
    }

    // condition wasn't met, keep processing here

    // finally return false so two() keeps going too
    return false;
}