job/rc/main/java/Singleton.java

public class SingletonPattern {
    // 单例模式实现示例
    private static SingletonPattern instance;
    
    private SingletonPattern() {}  // 私有构造函数
    
    public static SingletonPattern getInstance() {
        if (instance == null) {
            instance = new SingletonPattern();
        }
        return instance;
    }
    
    public void showMessage() {
        System.out.println("Singleton Pattern Demo");
    }
    
    // 程序入口
    public static void main(String[] args) {
        SingletonPattern singleton = SingletonPattern.getInstance();
        singleton.showMessage();
    }
}