finally

常见疑惑代码片段

（1）下面代码中的 finally 块会执行吗？

try {
  // do something
  System.exit(1);
} finally{
  System.out.println(“Print from finally”);
}

答案：不会。

（2）finally 会执行吗？

public static int test() {
    try {
        return 0;
    } finally {
        System.out.println("finally trumps return.");
    }
}

答案：

finally trumps return. 
0

（3）这个方法返回的值是 10 还是 12？

public static int getMonthsInYear() {
    try {
        return 10;
    } finally {
        return 12;
    }
}

答案：12

（4）执行顺序

try{
    int divideByZeroException = 5 / 0;
} catch (Exception e){
    System.out.println("catch");
    return;    // also tried with break; in switch-case, got same output
} finally {
    System.out.println("finally");
}

答案：

catch
finally

（5）赋值

public static void main(final String[] args) {
    System.out.println(test());
}

public static int test() {
    int i = 0;

    try {
        i = 2;
        return i;
    } finally {
        i = 12;
        System.out.println("finally trumps return.");
    }
}

结果：

finally trumps return.
2

（6）执行顺序

public static void main(String[] args) {
    System.out.println(Test.test());
}

public static int printX() {
    System.out.println("X");
    return 0;
}

public static int test() {
    try {
        return printX();
    } finally {
        System.out.println("finally trumps return... sort of");
    }
}

结果：

X
finally trumps return... sort of
0

不会执行 finally 的情况

触发了 System.exit()
触发了 Runtime.getRuntime().halt(exitStatus)
JVM Crash