<strong></strong><pre name="code" class="java"><strong>【餓漢式】</strong>

public class Single {

	private static Single single = new Single();
	private Single()
	{
		
	}
	public static Single getInstance(){
		return single;
	}
	
}

public class Demo {

	public static void main(String[] args) {

		Single s = Single.getInstance();
		Single s1 = Single.getInstance();
		System.out.println(s);
		System.out.println(s1);
	}

}
 

兩個變數地址相同。

總結：單例類

1.私有構造方法；

2.本類中建立物件；

3.對外提供獲取本類對像的方法；

單例類在程式碼上的體現：

餓漢式：此類一載入就建立物件；上為餓漢式；

【懶漢式】

<span style="font-size:18px;">public class Single {

	
	private Single(){}  <strong>1</strong>.

</span><pre name="code" class="java"><span style="white-space:pre"><span style="font-size:18px;">	</span></span>
 

<span style="font-size:18px;"><span style="white-space:pre">	</span>private static Single single = <strong>null; 2</strong></span>

<span style="font-size:18px;"> <span style="white-space:pre">		</span> return single;</span>
 

開發時用餓漢式；

面試一般問懶漢式；多執行緒操作，物件不唯一；

餓漢式單例程鞏固

<span style="font-size:18px;">public class SuperMan {
	private String name;

	private SuperMan(String name) {
		this.setName(name);
	}

	public static SuperMan superMan = new SuperMan("mj");

	public static SuperMan getInstance() {
		return superMan;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public void show() {
		System.out.println(name + "flay");
	}
}



public class Demo {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		SuperMan superMan = SuperMan.getInstance();
		System.out.println(superMan);
		superMan.show();
		superMan.setName("mjj");
		superMan.show();
	}

}</span>