易学设计模式九 单例模式(Singleton)
单例模式确保某一个类只有一个实例,并且自行实例化向整个系统提供这个实例
饿汉式
public class EagerSingleton {private static final EagerSingleton instance = new EagerSingleton();private EagerSingleton(){}public static EagerSingleton getInstance() {return instance;}}
public class LazySingleton {private static LazySingleton instance = null;private LazySingleton() {}synchronized public static LazySingleton getInstance() {if(instance == null) {instance = new LazySingleton();}return instance;}}
public class CmdTest {public static void main(String[] args) throws IOException {Process proc = Runtime.getRuntime().exec("notepad.exe");}}