java 異常抛出 throw 與 return

Posted 2020-09-02 --LP--

package 異常;  
 
public class TestException {  
    public TestException() {  
    }  
 
    boolean testEx() throws Exception {  
        boolean ret = true;  
        try {  
            ret = testEx1();  
        } catch (Exception e) {  
            e.printStackTrace();
            System.out.println("testEx, catch exception");  
            ret = false;  
            throw e;  
        } finally {  
            System.out.println("testEx, finally; return value=" + ret);  
            return ret;  
        }  
    }  
 
    boolean testEx1() throws Exception {  
        boolean ret = true;  
        try {  
            ret = testEx2();  
            if (!ret) {  
                return false;  
            }  
            System.out.println("testEx1, at the end of try");  
            return ret;  
        } catch (Exception e) {  
            e.printStackTrace();
            System.out.println("testEx1, catch exception");  
            ret = false;  
            throw e;  
        } finally {  
            System.out.println("testEx1, finally; return value=" + ret);  
            return ret;  
        }  
    }  
 
    boolean testEx2() throws Exception {  
        boolean ret = true;  
        try {  
            int b = 12;  
            int c;  
            for (int i = 2; i >= -2; i--) {  
                c = b / i;  
                System.out.println("i=" + i);  
            }  
//            return true;  
        } catch (Exception e) {
            e.printStackTrace();
            System.out.println("testEx2, catch exception");  
            ret = false;  
           //極其重要 throw 可以代替 return 若後面 finally 中是 return 調用此方法的將不會收到異常
           //（即catch裏面作爲結果抛出的異常被finally裏面的return覆蓋了）   若沒有return也沒有抛出某異常  則調用的將會接到此處抛出的異常並處理
            throw e;    
        } finally {  
            System.out.println("testEx2, finally; return value=" + ret);  
//            return ret;  
            throw new ArrayIndexOutOfBoundsException();
        }
//        System.out.println("執行中");
//        return false;
    }  
 
    public static void main(String[] args) {  
        TestException testException1 = new TestException();  
        try {  
            testException1.testEx();  
        } catch (Exception e) {  
            e.printStackTrace();  
            System.out.println("main");
        }  
    }  
}

 

結果

i=2
i=1
java.lang.ArithmeticException: / by zero
    at 異常.TestException.testEx2(TestException.java:48)
    at 異常.TestException.testEx1(TestException.java:25)
    at 異常.TestException.testEx(TestException.java:10)
    at 異常.TestException.main(TestException.java:71)
testEx2, catch exception
testEx2, finally; return value=false
java.lang.ArrayIndexOutOfBoundsException
    at 異常.TestException.testEx2(TestException.java:62)
    at 異常.TestException.testEx1(TestException.java:25)
    at 異常.TestException.testEx(TestException.java:10)
    at 異常.TestException.main(TestException.java:71)
testEx1, catch exception
testEx1, finally; return value=false
testEx, finally; return value=false

 

如果所有方法都层层上抛获取的异常，最终JVM会进行处理，处理也很简单，就是打印异常消息和堆栈信息

 

質料   http://www.cnblogs.com/to-creat/p/5688235.html