單例模式：確保某一個類只有一個實例，而且自行實例化并向整個系統提供這個實例。

package com.juno.SinglePattern; // 餓漢式單例，通用代碼，建議 public class SingletonOne {private static final SingletonOne instance = new SingletonOne();private SingletonOne() {}public static SingletonOne getInstance() {return instance;}public static void doSomething() {System.out.println("Singleton One do something~~");} }
package com.juno.SinglePattern; // 懶漢式單例 public class SingletonSecond {private static SingletonSecond instance = null;private SingletonSecond() {}public synchronized static SingletonSecond getInstance() {if (null == instance) {instance = new SingletonSecond();}return instance;}public static void doSomething() {System.out.println("Singleton Second do something~~");} }
package com.juno.SinglePattern;public class Singleton {public static void main(String[] args) {SingletonOne singletonOne = SingletonOne.getInstance();SingletonSecond singletonSecond = SingletonSecond.getInstance();singletonOne.doSomething();singletonSecond.doSomething();} }

總結

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