try、catch、finally与return的执行顺序问题

• finally一定会执行
• return以最后一次为准
• return后的finally是否修改了数据，得看具体类型

try{} catch(){}finally{} return

按照正常的顺序执行：有错会执行catch，finally都会执行，最后执行return。

    private static int returnInFinally_00(){
        int a ;
        try {
            System.out.println("try...");
            a = 3 / 0;
        } catch (Exception e){
            System.out.println("catch...");
        } finally {
            System.out.println("finally...");
            a = 2;
        }
        return 100;
    }
    // 100

try{ return; }catch(){} finally{} return

try中已经return，所以不再执行finally后面的return。

    private static int returnInFinally_01(){
        int a ;
        try{
            System.out.println("try...");
            a = 3 / 1;
            return a;
        } catch (Exception e){
            System.out.println("catch...");
        } finally {
            System.out.println("finally...");
            a = 2;
        }
        return 100;
    }
    // 3

try{ } catch(){return;} finally{} return

与上述情况类似

    private static int returnInFinally_02(){
        int a = 0;
        try{
            System.out.println("try...");
            a = 3 / 0;
        } catch (Exception e){
            System.out.println("catch...");
            return a;
        } finally {
            System.out.println("finally...");
            a = 2;
        }
        return a;
    }
    // 0

try{ return; }catch(){} finally{return;}

程序执行try块中return之前（包括return语句中的表达式运算）代码；再执行finally块，因为finally块中有return所以提前退出（这提前退出的意思是指：后面的代码都不会再执行了，所以就退出）。

    private static int returnInFinally_03(){
        int a ;
        try{
            System.out.println("try...");
            a = 3 / 1;
            return a;
        } catch (Exception e){
            System.out.println("catch...");
        } finally {
            System.out.println("finally...");
            a = 2;
            return a;
        }
        //return 100; 不可能执行此代码，编译器直接报错
    }
    // 2

try{} catch(){return;}finally{return;}

与上述类似

    private static int returnInFinally_04(){
        int a = 0;
        try{
            System.out.println("try...");
            a = 3 / 0;
        } catch (Exception e){
            System.out.println("catch...");
            return a ++;
        } finally {
            System.out.println("finally...");
            a ++;
            return a;
        }
    }
    // 2

try{ return;}catch(){return;} finally{return;}

同上述类似

    private static int returnInFinally_05(){
        int a = 1;
        try{
            System.out.println("try...");
            a = 3 / 0;
            return a;
        } catch (Exception e){
            System.out.println("catch...");
            return a ++;
        } finally {
            System.out.println("finally...");
            a ++;
            return a;
        }
    }
    // 3

return后在finally中修改值是否会影响结果？

问题回到传值还是传引用上啦，这里有疑问就再回去看看传值与传引用吧

    // 一个普通测试类
    private static class TestObject{
        private int x;

        public int getX() {
            return x;
        }

        public void setX(int x) {
            this.x = x;
        }
        // 覆盖toString
        @Override
        public String toString() {
            return "x = " + x;
        }
    }

    private static TestObject returnInFinally_06(){
        TestObject to = new TestObject();
        try{
            System.out.println("try...");
            to.setX(1);// 设为1
            return to;
        } catch (Exception e){
            System.out.println("catch...");
            to.setX(2);// 设为2
            return to;
        } finally {
            System.out.println("finally...");
            to.setX(3);// 最终设为3
        }
    }
    // try...
    // finally...
    // x = 3