Java 經典單例模式代碼

public class Singleton {
    private static Singleton uniqueInstance = null;
 
    private Singleton() {
       // Exists only to defeat instantiation.
    }
 
    public static Singleton getInstance() {
       if (uniqueInstance == null) {
           uniqueInstance = new Singleton();
       }
       return uniqueInstance;
    }
    // Other methods...
}