1、try塊中沒有拋出異常,try、catch和finally塊中都有return語句
| 12345678910111213141516 | public static int NoException(){ int i=10; try{ System.out.PRintln("i in try block is:"+i); return --i; } catch(Exception e){ --i; System.out.println("i in catch - form try block is:"+i); return --i; } finally{ System.out.println("i in finally - from try or catch block is:"+i); return --i; } } |
運行代碼:
| 12345 | public static void main(String[] args) { System.out.println("=============NoException=================="); System.out.println(NoException()); System.out.println("==============================="); } |
運行結果:
| 12345 | =============NoException==================i in try block is:10i in finally - from try or catch block is:98=============================== |
執行順序:
執行try塊,執行到return語句時,先執行return的語句,–i,但是不返回到main方法,執行finally塊,遇到finally塊中的return語句,執行–i,并將值返回到main方法,這里就不會再回去返回try塊中計算得到的值。
結論:try-catch-finally都有return語句時,沒有異常時,返回值是finally中的return返回的。
2.try塊中沒有拋出異常,僅try和catch中有return語句
| 123456789101112131415161718 | public static int NoException1(){ int i=10; try{ System.out.println("i in try block is:"+i); return --i; } catch(Exception e){ --i; System.out.println("i in catch - form try block is:"+i); return --i; } finally{ System.out.println("i in finally - from try or catch block is:"+i); --i; System.out.println("i in finally block is:"+i); //return --i; }} |
運行結果:
| 123456 | =============NoException1==================i in try block is:10i in finally - from try or catch block is:9i in finally block is:89=============================== |
執行順序:
try中執行完return的語句后,不返回,執行finally塊,finally塊執行結束后,返回到try塊中,返回i在try塊中最后的值。
結論:try-catch都有return語句時,沒有異常時,返回值是try中的return返回的。
3.try塊中拋出異常,try、catch和finally中都有return語句
| 1234567891011121314151617181920 | public static int WithException(){ int i=10; try{ System.out.println("i in try block is:"+i); i = i/0; return --i; } catch(Exception e){ System.out.println("i in catch - form try block is:"+i); --i; System.out.println("i in catch block is:"+i); return --i; } finally{ System.out.println("i in finally - from try or catch block is--"+i); --i; System.out.println("i in finally block is--"+i); return --i; }} |
執行結果:
| 12345678 | =============WithException==================i in try block is:10i in catch - form try block is:10i in catch block is:9i in finally - from try or catch block is--8i in finally block is--76=============================== |
執行順序:
拋出異常后,執行catch塊,在catch塊的return的–i執行完后,并不直接返回而是執行finally,因finally中有return語句,所以,執行,返回結果6。
結論:
try塊中拋出異常,try、catch和finally中都有return語句,返回值是finally中的return。
4.try塊中拋出異常,try和catch中都有return語句
| 1234567891011121314151617 | public static int WithException1(){ int i=10; try{ System.out.println("i in try block is:"+i); i=i/0; return --i; }catch(Exception e){ System.out.println("i in catch - form try block is:"+i); return --i; }finally{ System.out.println("i in finally - from try or catch block is:"+i); --i; System.out.println("i in finally block is:"+i); //return i; }} |
執行結果:
| 1234567 | =============WithException1==================i in try block is:10i in catch - form try block is:10i in finally - from try or catch block is:9i in finally block is:89=============================== |
執行順序:
拋出異常后,執行catch塊,執行完finally語句后,依舊返回catch中的執行return語句后的值,而不是finally中修改的值。
結論:
返回的catch中return值。
5.try、catch中都出現異常,在finally中有返回
| 1234567891011121314151617181920 | public static int WithException2(){ int i=10; try{ System.out.println("i in try block is:"+i); i=i/0; return --i; } catch(Exception e){ System.out.println("i in catch - form try block is:"+i); int j = i/0; return --i; } finally{ System.out.println("i in finally - from try or catch block is:"+i); --i; --i; System.out.println("i in finally block is:"+i); return --i;} |
執行結果:
| 1234567 | =============WithException2==================i in try block is:10i in catch - form try block is:10i in finally - from try or catch block is:10i in finally block is:87=============================== |
執行順序:
try塊中出現異常到catch,catch中出現異常到finally,finally中執行到return語句返回,不檢查異常。
結論:
返回finally中return值。
6、只在函數最后出現return語句
| 12345678910111213141516171819202122 | public static int WithException3(){ int i=10; try{ System.out.println("i in try block is:"+i); i=i/0; //return --i; } catch(Exception e){ System.out.println("i in catch - form try block is:"+i); //int j = i/0; //return --i; } finally{ System.out.println("i in finally - from try or catch block is:"+i); --i; --i; System.out.println("i in finally block is:"+i); //return --i; } return --i;} |
執行結果:
| 1234567 | =============WithException3==================i in try block is:10i in catch - form try block is:10i in finally - from try or catch block is:10i in finally block is:87=============================== |
總體結論:
結論一:
return語句并不是函數的最終出口,如果有finally語句,這在return之后還會執行finally(return的值會暫存在棧里面,等待finally執行后再返回)結論二:
finally里面不建議放return語句,根據需要,return語句可以放在try和catch里面和函數的最后。可行的做法有四: (1)return語句只在函數最后出現一次。 (2)return語句僅在try和catch里面都出現。 (3)return語句僅在try和函數的最后都出現。 (4)return語句僅在catch和函數的最后都出現。 注意,除此之外的其他做法都是不可行的,編譯器會報錯。
轉載自:http://qing0991.blog.51cto.com/1640542/1387200
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