檢視 SCJP 1.6版考題 050 的原始碼

 1. public abstract class Shape{
 2.   private int x;
 3.   private int y;
 4.   public abstract void draw();
 5.   public void setAnchor(int x, int y){
 6.     this.x = x;
 7.     this.y = y;
 8.   }
 9. }
 
 
 Which two classes use the Shape class correctly? (Choose two.)
 
  A.
  public class Circle implements Shape{
    private in radius;
  }
  
  B.
  public abstract class Circle extends Shape{
    private in radius;
  }
  C.
  public class Circle extends Shape{
    private in radius;
    public void draw();
  } 
  
  D.
  public abstract class Circle implements Shape{
    private in radius;
    public void draw();
  }
  E.
  public class Circle extends Shape{
    private in radius;
    public void draw(){/* code here */}
  }
  
  F.
  public abstract class Circle implements Shape{
    private in radius;
    public void draw(){/* code here */}
  }
 

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<span style="font-size:medium;">解答</span>

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<span style="font-size: medium;">Ans: B E   </span>

<span style="font-size:medium;"> 解說:
 一個類別中若有抽象方法(沒有實作)，則類別必須為abstract，Circle繼承抽象類別Shape，
 若Circle不為抽象類別，必須對繼承自Shape的抽象方法補上實作
 使用implements必須針對介面的類別。(A/D/F錯)

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{{SCJP 1.6版考題講解}}