dd

Extract Local Variable 自动生成返回值对象 alt+shift+L

查询快键键Ctrl+Shift+L

先输入sysout，然后输入辅助快捷键：Alt+/，这样就可以自动生成：System.out.println();

shift+ alt+ s  override/implement methods 重写方法

 ctrl + t 查看子类

泛型 类名后<T>

Java Map 接口

import java.util.*;

public class CollectionsDemo {

   public static void main(String[] args) {
      Map m1 = new HashMap(); 
      m1.put("Zara", "8");
      m1.put("Mahnaz", "31");
      m1.put("Ayan", "12");
      m1.put("Daisy", "14");
      System.out.println();
      System.out.println(" Map Elements");
      System.out.print("	" + m1);
   }
}



Map Elements
        {Mahnaz=31, Ayan=12, Daisy=14, Zara=8}