try catch finally，try里有return，finally还执行么？

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finally是在try的语句执行之后并且try的return返回之前执行的（此时并没有返回运算后的值，而是先把要返回的值保存起来，管finally中的代码怎么样，返回的值都不会改变，任然是之前保存的值，如test1测试代码），return的时候是复制了一个变量然后返回，所以之后finally操作的变量如果是基本类型的话不会影响返回值。 但是如果返回值是引用类型的话，因为指向同一个对象所以还是有影响的。在try块中有System.exit(0);这样的语句，System是一个Java类，调用exit(0)方法终止虚拟机也就是退出你的Java程序，括号里面的是参数，进程结束的返回值，这样finally语句也不会被执行到。

 public static String test1() {        try {            System.out.println("try block");           return test12();      } finally {           System.out.println("finally block");       }  }  public static String test12() {       System.out.println("Start executing the ruturn statement in try");       return "try requires return statements";   }

运行的结果：(验证了finally是在开始执行try中要reuturn的语句之后并且try需要return的语句返回之前执行的。

try blockStart executing the ruturn statement in tryfinally blocktry requires return statement

finally块中有return语句的会覆盖try块中的return返回。如test2测试代码。

public static String test2() {String statements = "requires return statements";try {System.out.println("try block");return "try  " + statements;} catch (Exception e) {System.out.println("catch block");} finally {System.out.println("finally block");return "finally  " + statements;}}

运行结果：

try blockfinally blockfinally requires return statements

如果finally语句中没有return语句覆盖返回值，按照try块中的return返回。如test3测试代码

public static String test3() {String statements = "requires return statements";try {System.out.println("try block");return "try " + statements;} catch (Exception e) {System.out.println("catch block");} finally {System.out.println("finally block");statements = "finally " + statements;}return "Other statements ";}

运行结果：

try blockfinally blocktry requires return statements

finally操作的变量如果是基本类型的话不会影响返回值，finally操作的变量如果返回值是引用类型的话，因为指向同一个对象所以还是有影响的。如test4测试代码

 public static Map<String, String> test4() {        Map<String, String> map = new HashMap<String, String>();        map.put("KEY", "INIT");                 try {            map.put("KEY", "TRY");            return map;        }        catch (Exception e) {            map.put("KEY", "CATCH");        }        finally {            map.put("KEY", "FINALLY");            map = null;        }                 return map;    }

运行结果：

{KEY=FINALLY}

try块里的return语句在异常的情况下不会被执行。如test5测试代码

public static String test5() {int b = 20;String statements = "requires return statements";try {System.out.println("try block");b = b / 0;return "try " + statements;} catch (Exception e) {b += 15;System.out.println("catch block");} finally {System.out.println("finally block");if (b > 25) {System.out.println("b>25, b = " + b);}b += 50;}return "Other statements ";}

运行结果：

try blockcatch blockfinally blockb>25, b = 35Other statements

当发生异常后，catch中的return执行情况与未发生异常时try中return的执行情况完全一样.如test6测试代码

public static String test6() {          int b = 20;          String statements = "requires return statements";        try {              System.out.println("try block");                            b = b /0;               return  "try " + statements;        } catch (Exception e) {          b += 15;            System.out.println("catch block");              return  "catch " + statements;          } finally {              System.out.println("finally block");                if (b > 25) {                  System.out.println("b>25, b = " + b);              }              b += 50;          }      }

运行结果：

try blockcatch blockfinally blockb>25, b = 35catch requires return statements

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