Overload

1. Overload Overload (多載, 重載) --只要method signature(方法簽章) 不一樣, 雖然名稱一樣, 也可以成立 Signature: 方法名稱雖一樣 但引數個數不一樣 或 引數資料型態對應不一樣

2. Method的語法

3. Declaring Classes(宣告類別) • 宣告類別: 告訴他人我這個類別將有哪些屬性及方法 • extends: 繼承, 下面例子MyClass可以延用MySuperClass的方法implements實作, 下面例子MyClass要將YourInterface中所宣告的方法, 完成定義

4. Declaring Member Variables (宣告變數及方法) • Member variables in a class(在類別大括號之間宣告的變數稱為)—these are called fields(屬性). • Variables in a method or block of code(在方法-及副程式大括號之間宣告的變數稱為)—these are called local variables 區域變數(). • Variables in method declarations(在方法-及副程式圓括號之間宣告的變數稱為)—these arecalled parameters(參數). • Access Modifiers(修飾元)  public modifier(公用)—the field is accessible from all classes 所有其他類別皆可用到.  private modifier(私有)—the field is accessible only within its own class 只有自己的類別內部的成員, 如屬性和方法, 才能用.

5. 建構元Constructor • 建構元: 建立物件的方法 • 建構元是特殊的方法, 不傳回任何型態, 也不傳回 void  • 若類別本身沒有建構元, compiler 會給予一個預設建構元=> 類別名稱(){}

6. abstract class(抽象類別) • 抽象類別必須以abstract宣告 • 類別其中有一個方法為abstract =>沒有實作{}, 就必須宣告為abstract. • 但也可全部方法都不是abstract • abstract class主要不讓 使用者建立物件 • 抽象類別不能被New起來 (ch11, p11) • 繼承抽象類別的類別必須將方法補齊 (ch11, p8)

7. Override&Overload 練習http://192.192.246.169/~wells/wiki/index.php/SCJP_1.6%E7%89%88%E8%80%83%E9%A1%8C_012

8. Override&Overload 練習 • http://nikojava.wordpress.com/2008/10/10/free-scjp-mock-exams/

9. Override 練習 • Explanation: • An overriding method can throw the same exceptions(相同的例外), narrower exceptions(範圍較小的例外), or no exceptions (無例外)and can throw any runtime exceptions(可以丟出RUNTIME例外)whether they were listed in the overridden method or not. • An overriding method cannot reduce the access scope of the overridden method but can widen it.

10. Override 練習

11. Override 練習http://www.tutorialspoint.com/java/java_overriding.htm

12. Override 練習 import java.io.*; class Test { public void display() throws IOException { } } public class Demo extends Test { public void display() throws Exception { } // throwing super class exception } //error, why

13. Override 練習 import java.io.*; class Test { public void display() throws IOException { } } public class Demo extends Test { public void display() throws IOException { } }