try-catch-finally面试题

try catch finally 执行顺序面试题总结

执行顺序

今天牛客网遇到这个题目，做对了，但是下面的评论却很值得看看

public class TestTry {

    public int add(int a, int b){
        try {
            return a + b;
        } catch (Exception e) {
            System.out.println("catch语句");
        } finally {
            System.out.println("finally语句");
        }

        return 0;
    }
    public static void main(String[] args) {
        TestTry testTry = new TestTry();
        System.out.println(testTry.add(14, 15));
    }
}

这个题目答案是

finally语句
29

那么为什么是这样呢？

程序执行到try{}语句中的return方法时，它会干这么一件事，将要返回的结果存储到一个临时栈中，然后程序不会立即返回，而是去执行finally{}中的程序，等finally{}执行完成之后再返回

下面这个

public class Test02 {

    public int add(int a){
        try {
            a ++;
            System.out.println("try a = " + a);
            return a;
        } catch (Exception e) {
            a ++;
            System.out.println("catch a = " + a);
            return a;
        } finally {
            a = 10;
            System.out.println("finally a = " + a);
        }
    }
    public static void main(String[] args) {
        Test02 test02 = new Test02();
        System.out.println(test02.add(0));
    }
}

结果为

try a = 1
finally a = 10
1

下面这个

public class Test03 {

    public int add(int a){
        try {
            a ++;
            System.out.println("try a = " + a);
            return a;
        } catch (Exception e) {
            a ++;
            System.out.println("catch a = " + a);
            return a;
        } finally {
            a = 10;
            System.out.println("finally a = " + a);
            return a;
        }
    }
    public static void main(String[] args) {
        Test03 test03 = new Test03();
        System.out.println(test03.add(0));
    }

}

可以看到，是从finally语句块中返回的

try a = 1
finally a = 10
10

下面这个有异常的情况下

public class Test04 {
    public int add(int a){
        try {
            a ++;
            int m = a / 0;
            System.out.println("try a = " + a);
            return a;
        } catch (Exception e) {
            a ++;
            System.out.println("catch a = " + a);
            return a;
        } finally {
            a = 10;
            System.out.println("finally a = " + a);
            return a;
        }
    }

    public static void main(String[] args) {
        Test04 test04 = new Test04();
        System.out.println(test04.add(0));
    }
}

catch a = 2
finally a = 10
10

可以看到，因为finally中有return语句，try、catch中的异常被消化掉了，屏蔽了异常的发生，这与初期使用try、catch的初衷是相违背的