单身java模式

Question

我仍然可以通过使用构造函数实例化,虽然在类定义中它已被声明为私有构造函数??? 这是代码片段:

public class Singleton {

  private static Singleton instance;
  private String name;

  /* Private constructor prevents other classes from instantiating */
  private Singleton(String name) {
    this.name = name;
    // Optional code
  }

  /*
   * Static factory method that creates instance instead of constructor.
   * Synchronization helps to block any attempt to instantiate from simultaneous
   * thread hence break concept of singleton.
   * This method uses a technique known as lazy instantiation.
   */
  public static synchronized Singleton getInstance(String name) {
    if (instance == null) {
      instance = new Singleton(name);
    }
    return instance;
  }

  /* Override Object clone method to avoid cloning */
  @Override
  public Object clone() throws CloneNotSupportedException {
    throw new CloneNotSupportedException();
  }

  public String getName() {
    return name;
  }

  /* Example of using singleton object */
  public static void main(String[] args) {
    Singleton a = new Singleton("Hoang");
    Singleton b = new Singleton("Shiha");
    System.out.println(a.getName());
    System.out.println(b.getName());
  }

Answer 1

您仍然可以实例化它,因为在同一个类中的测试main()方法可以访问私有构造函数:private表示"仅对此类可用".

把你的考试放在另一堂课上,你会得到你期望的.