单例模式

测试.png

饿汉式单例模式.png

懒汉式单例模式.png

/*

• 懒汉式单例模式的写法
• */
  public class SinglePattern {
  // 私有构造方法
  private SinglePattern(){}
  // 定义一个类变量用于接收该类对象
  private static SinglePattern singlePatternDemo;
  // 对外提供一个方法,并判断该类是否被创建过,如果没有就创建返回,如果已经创建过就直接返回
  public static SinglePattern getInstance(){
  if (singlePatternDemo==null){
  //第一次创建
  singlePatternDemo = new SinglePattern();
  }
  return singlePatternDemo;
  }
  }

/*

• 饿汉式单例模式
• */
  public class SinglePatternOther {
  //私有构造方法
  private SinglePatternOther(){}
  // 创建一个类变量接收当前类的类对象
  private static SinglePatternOther singlePatternOtherDemo = new SinglePatternOther();

//对外提供一个方法将类对象返回
public static SinglePatternOther getInstant(){
return singlePatternOtherDemo;
}
}

public class Main {
public static void main(String[] args) {
System.out.println(SinglePattern.getInstance());
System.out.println(SinglePattern.getInstance());
System.out.println(SinglePattern.getInstance());
System.out.println(SinglePattern.getInstance());
System.out.println(SinglePattern.getInstance());
System.out.println(SinglePatternOther.getInstant());
System.out.println(SinglePatternOther.getInstant());
System.out.println(SinglePatternOther.getInstant());
System.out.println(SinglePatternOther.getInstant());
System.out.println(SinglePatternOther.getInstant());

}

}