java中finally与return的测试方法

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直入正题，测试程序如下，看执行结果和你想的是否一致？

public class ReturnTest {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);}}}

结果如下：

=============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 ===============================

很好理解了。

#结论：

在try catch块里return的时候，finally也会被执行。

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。

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：

最好把return放到方法尾而不要在try cath 里return

不要在try catch块和finally块里都包含return

如果在try catch块里return, 则不要在finally块里操作被return的变量

转载于:https://my.oschina.net/u/2391658/blog/706512

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