try catch throw finally的执行顺序

在调整一个项目功能的时候，需要在现有的代码逻辑上做改动，现有功能的逻辑是try-catch 异常后在catch中打印了日志，后需将异常throw出来

我增加的逻辑中需要增加 finally操作，那么这个throw操作和finally操作的顺序是什么样的呢， 增加了finally后会影响throw出异常吗，所以就针对这块做了写测试

（1）没有return，没有异常的场景

public class ExceptionTest {

    static void testEx01() throws Exception {
        try {
 System.out.println("testEx,successfully");         } catch (Exception e) {
            System.out.println("testEx, catch exception");
            throw e;
        } finally {
 System.out.println("testEx, finally");         }

    }

    public static void main(String[] args) throws Exception {
        testEx01();    }

}

执行结果：

testEx,successfully
testEx, finally

结论：

执行try的逻辑后，执行finally的逻辑

——————————————————————————————————————————————————————————————————————————————————————————————————————

（2）没有return值，有异常的场景

 

static void testEx01() throws Exception {
    try {
        int ret = 12/0;
        System.out.println("testEx,successfully");
    } catch (Exception e) {
        System.out.println("testEx, catch exception");
        throw e;
    } finally {
        System.out.println("testEx, finally");
    }

}

执行结果：

testEx, catch exception
testEx, finally
Exception in thread "main" java.lang.ArithmeticException: / by zero
    at com.jd.ldop.logtools.ExceptionTest.testEx01(ExceptionTest.java:11)
    at com.jd.ldop.logtools.ExceptionTest.main(ExceptionTest.java:23)

Process finished with exit code 1

结论：

执行catch代码的逻辑，抛出异常，执行finally的逻辑

——————————————————————————————————————————————————————————————————————————————————————————————————————

 

（2）有return值，没有异常的场景,finally中有return值

 catch中 return 和 throw不可以同时存在，以下场景编译不通过

    static int testEx01() throws Exception {
        try {
            int ret = 12/0;
            System.out.println("testEx,successfully");
            return 111;
        } catch (Exception e) {
            System.out.println("testEx, catch exception");
            throw e;
            return 222;
        } finally {
            System.out.println("testEx, finally");
            return 333;
        }

    }

 

 

 

去除 catch中return

 

public class ExceptionTest {

    static int testEx01() throws Exception {
        try {
            int ret = 12 / 1;
 System.out.println("testEx,successfully");
            return 111;
        } catch (Exception e) {
            System.out.println("testEx, catch exception");
            throw e;
        } finally {
 System.out.println("testEx, finally");
            return 333;         }

    }

    public static void main(String[] args) throws Exception {
        System.out.println(testEx01());
    }

}

执行结果：

testEx,successfully
testEx, finally
333

Process finished with exit code 0

结论：

执行try主流程逻辑，finally中有return的时候，会以finally中的return结果为准，其他的都将失效

——————————————————————————————————————————————————————————————————————————————————————————————————————

 

（3）有return值，有异常，finally中有return值的场景

public class ExceptionTest {

    static int testEx01() throws Exception {
        try {
            int ret = 12 / 0;             System.out.println("testEx,successfully");
            return 111;
        } catch (Exception e) {
 System.out.println("testEx, catch exception");
            throw e;
        } finally {
 System.out.println("testEx, finally");
            return 333;         }

    }

    public static void main(String[] args) throws Exception {
        System.out.println(testEx01());
    }

}

执行结果：

testEx, catch exception
testEx, finally
333

Process finished with exit code 0

结论：

从执行结果看，最终是返回了finally中的返回值，catch中代码执行了，但是异常并没有throw出来，这个异常被忽略了

——————————————————————————————————————————————————————————————————————————————————————————————————————

 

（4）有return值，有异常，finally中没有return值的场景

 

public class ExceptionTest {

    static int testEx01() throws Exception {
        try {
            int ret = 12 / 0;
            System.out.println("testEx,successfully");
            return 111;
        } catch (Exception e) {
            System.out.println("testEx, catch exception");
            throw e;
        } finally {
            System.out.println("testEx, finally");
        }

    }
    public static void main(String[] args) throws Exception {
        System.out.println(testEx01());
    }
}

执行结果：

testEx, catch exception
testEx, finally
Exception in thread "main" java.lang.ArithmeticException: / by zero
    at com.jd.ldop.logtools.ExceptionTest.testEx01(ExceptionTest.java:11)
    at com.jd.ldop.logtools.ExceptionTest.main(ExceptionTest.java:24)

Process finished with exit code 1

 

结论：

在finally没有返回值的场景中，异常会被抛出来，最终也是没有返回值的，因为运行时异常了

 

所以在finally中没有返回值的异常场景下，在catch代码块和finally代码块中去设置 返回变量的值是没有意义的，比如说如下：

 

 执行结果是和上面一样的：

testEx, catch exception
testEx, finally
Exception in thread "main" java.lang.ArithmeticException: / by zero
    at com.jd.ldop.logtools.ExceptionTest.testEx01(ExceptionTest.java:12)
    at com.jd.ldop.logtools.ExceptionTest.main(ExceptionTest.java:27)

Process finished with exit code 1