Java深入学习23:try catch finally执行和返回逻辑

Posted 2020-11-27 我不吃番茄

Java深入学习23:try catch finally执行和返回逻辑

 

先说结论：

　　一般逻辑，先执行try语句；如果有异常，则继续执行catch语句；如果有finally语句，则执行finally语句；

　　任何执行try 或者catch中的return语句之前，如果finally存在的，都会先执行finally语句；

　　如果finally中有return语句，那么程序就在finally中return了，所以finally中的return是一定会被return的，否则

 

源码示例：

public class TryCatchTest {

    public static String testNormalWithFinally(){

        try {
            int i = 0/1;
            System.out.println("this is try block");
            return "return try";
        } catch (Exception e) {
            e.printStackTrace();
            System.out.println("this is catch block");
            return "return catch";
        } finally {
            System.out.println("this is finally block");
            return "return finally ";
        }

    }

    public static String testExceptionWithFinally(){

        try {
            int j = 1/0;
            System.out.println("this is ctry block");
            return "return try";
        } catch (Exception e) {
            e.printStackTrace();
            System.out.println("this is catch block");
            return "return catch";
        } finally {
            System.out.println("this is finally block");
            return "return finally ";
        }

    }
    public static String testNormalWithoutFinallyReturn(){

        try {
            int i = 0/1;
            System.out.println("this is try block");
            return "return try";
        } catch (Exception e) {
            e.printStackTrace();
            System.out.println("this is catch block");
            return "return catch";
        } finally {
            System.out.println("this is finally block");
        }

    }
    public static String testExceptionWithoutFinallyReturn(){

        try {
            int j = 1/0;
            System.out.println("this is ctry block");
            return "return try";
        } catch (Exception e) {
            e.printStackTrace();
            System.out.println("this is catch block");
            return "return catch";
        } finally {
            System.out.println("this is finally block");
        }

    }

    public static void main(String[] args) {
        System.out.println("-------------testNormalWithFinally-------------------");
        System.out.println(testNormalWithFinally());
        System.out.println("----------------testExceptionWithFinally----------------");
        System.out.println(testExceptionWithFinally());
        System.out.println("---------------testNormalWithoutFinallyReturn-----------------");
        System.out.println(testNormalWithoutFinallyReturn());
        System.out.println("--------------testExceptionWithoutFinallyReturn------------------");
        System.out.println(testExceptionWithoutFinallyReturn());
    }
}
--------------------------------日志输出---------------------------------------------
-------------testNormalWithFinally-------------------
java.lang.ArithmeticException: / by zero
this is try block
    at interview.trycatchfinally.TryCatchTest.testExceptionWithFinally(TryCatchTest.java:32)
this is finally block
return finally 
    at interview.trycatchfinally.TryCatchTest.main(TryCatchTest.java:80)
----------------testExceptionWithFinally----------------
java.lang.ArithmeticException: / by zero
this is catch block
this is finally block
return finally 
    at interview.trycatchfinally.TryCatchTest.testExceptionWithoutFinallyReturn(TryCatchTest.java:63)
---------------testNormalWithoutFinallyReturn-----------------
this is try block
    at interview.trycatchfinally.TryCatchTest.main(TryCatchTest.java:84)
this is finally block
return try
--------------testExceptionWithoutFinallyReturn------------------
this is catch block
this is finally block
return catch