return遇到finally

 public class Test {

     public static void main(String[] args) {
         System.out.println("=============test1==================");
         System.out.println(test1());
         System.out.println("===============================");

         System.out.println("=============test1_1==================");
         System.out.println(test1_1());
         System.out.println("===============================");

         System.out.println("\n============test2===================");
         System.out.println(test2());
         System.out.println("===============================");

         System.out.println("\n============test2_1===================");
         System.out.println(test2_1());
         System.out.println("===============================");

         System.out.println("\n============test3===================");
         System.out.println(test3());
         System.out.println("===============================");

         System.out.println("\n============test3_1===================");
         System.out.println(test3_1());
         System.out.println("===============================");
     }

     public static String test1() {
         String a = "in try";

         try{
             return a;
         } catch ( Exception e ) {

         } finally {
             a = "in finally";
             System.out.println("do finally");
         }

         return a;
     }

     public static String test1_1() {
         String a = "in try";

         try{
             return a;
         } catch ( Exception e ) {

         } finally {
             a = "in finally";
             System.out.println("do finally");
             return a;
         }
     }

     public static int test2() {
         int a = 1;

         try{
             return a;
         } catch ( Exception e ) {

         } finally {
             a = 2;
             System.out.println("do finally");
         }

         return a;
     }

     public static int test2_1() {
         int a = 1;

         try{
             return a;
         } catch ( Exception e ) {

         } finally {
             a = 2;
             System.out.println("do finally");
             return a;
         }
     }

     public static Helper test3() {
         Helper a = new Helper();
         a.a = 1;

         try{
             return a;
         } catch ( Exception e ) {

         } finally {
             a.a = 2;
             System.out.println("do finally");
         }

         return a;
     }

     public static Helper test3_1() {
         Helper a = new Helper();
         a.a = 1;

         try{
             return a;
         } catch ( Exception e ) {

         } finally {
             a.a = 2;
             System.out.println("do finally");
             return a;
         }
     }

     static class Helper {
         int a;

         public String toString() {
             return String.valueOf(a);
         }
     }
 }

运行的结果:

 =============test1==================
 do finally
 in try
 ===============================
 =============test1_1==================
 do finally
 in finally
 ===============================

 ============test2===================
 do finally
 1
 ===============================

 ============test2_1===================
 do finally
 2
 ===============================

 ============test3===================
 do finally
 2
 ===============================

 ============test3_1===================
 do finally
 2
 ===============================

结论：

1. 在try catch块里return的时候，finally也会被执行。
2. return 语句会把后面的值复制到一份用来返回，如果return的是基本类型的，finally里对变量的改动将不起效果，如果return 的是引用类型的，改动将可以起效果。
3. finally里的return语句会把try catch块里的return语句效果给覆盖掉。

看来return语句并不一定都是函数的出口，执行return时，只是把return后面的值复制了一份到返回值变量里去了。看来最佳实践是：

1. 最好把return放到方法尾而不要在try cath 里return
2. 不要在try catch块和finally块里都包含return
3. 如果在try catch块里return, 则不要在finally块里操作被return的变量

文章来自：http://www.360doc.com/content/11/0905/19/1542811_146016871.shtml