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直入正題，測試程序如下，看執行結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);}}}

結果如下：

=============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。

#結論：

在try catch塊里return的時候，finally也會被執行。

return 語句會把后面的值復制到一份用來返回，如果return的是基本類型的，finally里對變量的改動將不起效果，如果return 的是引用類型的，改動將可以起效果。

finally里的return語句會把try catch塊里的return語句效果給覆蓋掉。

看來return語句并不一定都是函數的出口，執行return時，只是把return后面的值復制了一份到返回值變量里去了。看來最佳實踐是：

最好把return放到方法尾而不要在try cath 里return

不要在try catch塊和finally塊里都包含return

如果在try catch塊里return, 則不要在finally塊里操作被return的變量

轉載于:https://my.oschina.net/u/2391658/blog/706512

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