Java中try，return ，finally，throw使用总结：

Java中try，return ，finally，throw使用总结：

 

（1）      当try中抛出异常且catch中有return语句，finally中没有return语句，java先执行catch中非return语句，再执行finally语句，最后执行catch中return语句。详见情况一。

（2）      当try中抛出异常且catch中有return语句，finally中也有return语句，java先执行catch中非return语句，再执行finally中非return语句，最后执行finally中return语句，函数返回值为finally中返回的值。详见情况二。

（3）      Throw（无能是catch中还是非catch中）后面不能再跟code，否则编译不能通过。详见下面情况三，四，五。

Return，finally总结：

情况一，代码如下：

public class Test {

public int testTry(){

       FileInputStreamfi=null;

      

       try{

           fi=newFileInputStream("");

          

       }catch(FileNotFoundExceptionfnfe){

            System.out.println("this isFileNotFoundException");

            return 1;

       }catch(SecurityExceptionse){

           System.out.println("thisis SecurityException");

       }finally{

           System.out.println("thisis finally");

       }

       return0;

}

 

public static void main(String[] args) {

Test t=new Test();

       System.out.println(t.testTry());

}

}

Output：

this is FileNotFoundException

this is finally

1

 

情况二，代码修改如下：

public class Test {

public int testTry(){

       FileInputStreamfi=null;

      

       try{

           fi=newFileInputStream("");

          

       }catch(FileNotFoundExceptionfnfe){

            System.out.println("this is FileNotFoundException");

            return 1;

       }catch(SecurityExceptionse){

           System.out.println("thisis SecurityException");

       }finally{

           System.out.println("thisis finally");

            return 3;

       }

       //return0;

}

 

public static void main(String[] args) {

Test t=new Test();

       System.out.println(t.testTry());

}

}

Output：

this is FileNotFoundException

this is finally

3

----------------------------------------------------

Return throw总结：

情况三：

public class Test {

    publicstatic void main(String[] args) {

       Testt=new Test();

       try{

       System.out.println(t.testTry());

       }catch(Exceptione){

           System.out.println("thisis exception");

       }

      

    }

    publicint testTry()throws Exception{

       FileInputStreamfi=null;

      

       try{

           fi=newFileInputStream("");

          

       }catch(FileNotFoundExceptionfnfe){

            //System.out.println("this is FileNotFoundException"); 

           thrownew Exception();

           return 1;

       }catch(SecurityExceptionse){

           System.out.println("thisis SecurityException");

       }finally{

           System.out.println("thisis finally");

       }

       return0;

    }

}

 

>javac Test.java

Test.java:22:无法访问的语句

                     Return 1;

 

情况四：

public class Test {

    publicstatic void main(String[] args) {

       Testt=new Test();

       try{

       System.out.println(t.testTry());

       }catch(Exceptione){

           System.out.println("thisis exception");

       }

      

    }

    publicint testTry()throws Exception{

       FileInputStreamfi=null;

      

       try{

           fi=newFileInputStream("");

          

       }catch(FileNotFoundExceptionfnfe){

            //System.out.println("this isFileNotFoundException"); 

           thrownew Exception();

           System.out.println("afterthrow exception");

          // return 1;

       }catch(SecurityExceptionse){

           System.out.println("thisis SecurityException");

       }finally{

           System.out.println("thisis finally");

       }

       return0;

    }

}

>javac Test.java

Test.java:22:无法访问的语句

                    System.out.println("this isSecurityException");

 

情况五：

public class Test {

    publicstatic void main(String[] args) {

       Testt=new Test();

       try{

       t.testTry();

       }catch(Exceptione){

           System.out.println("thisis exception");

       }

      

    }

    publicvoid testTry()throws Exception{

       thrownew Exception();

       System.out.println("thisis testTry method");

    }

}

>javac Test.java

Test.java:22:无法访问的语句

                    System.out.println("thisis testTry method");