try catch throw finally的執行順序

在調整一個項目功能的時候，需要在現有的代碼邏輯上做改動，現有功能的邏輯是try-catch 異常后在catch中打印了日志，后需將異常throw出來

我增加的邏輯中需要增加 finally操作，那么這個throw操作和finally操作的順序是什么樣的呢， 增加了finally后會影響throw出異常嗎，所以就針對這塊做了寫測試

（1）沒有return，沒有異常的場景

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();    }

}

執行結果：

testEx,successfully
testEx, finally

結論：

執行try的邏輯后，執行finally的邏輯

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

（2）沒有return值，有異常的場景

 

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");
    }

}

執行結果：

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

結論：

執行catch代碼的邏輯，拋出異常，執行finally的邏輯

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

 

（2）有return值，沒有異常的場景,finally中有return值

 catch中 return 和 throw不可以同時存在，以下場景編譯不通過

    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());
    }

}

執行結果：

testEx,successfully
testEx, finally
333

Process finished with exit code 0

結論：

執行try主流程邏輯，finally中有return的時候，會以finally中的return結果為准，其他的都將失效

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

 

（3）有return值，有異常，finally中有return值的場景

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());
    }

}

執行結果：

testEx, catch exception
testEx, finally
333

Process finished with exit code 0

結論：

從執行結果看，最終是返回了finally中的返回值，catch中代碼執行了，但是異常並沒有throw出來，這個異常被忽略了

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

 

（4）有return值，有異常，finally中沒有return值的場景

 

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());
    }
}

執行結果：

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

 

結論：

在finally沒有返回值的場景中，異常會被拋出來，最終也是沒有返回值的，因為運行時異常了

 

所以在finally中沒有返回值的異常場景下，在catch代碼塊和finally代碼塊中去設置 返回變量的值是沒有意義的，比如說如下：

 

 執行結果是和上面一樣的：

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