Java 使用HashMap基本操作

青旅半醒 2022-10-01 00:36 189阅读 0赞

代码

package beginnersbook.com;
    import java.util.HashMap;
    import java.util.Map;
    import java.util.Iterator;
    import java.util.Set;
    public class Details {
    
       public static void main(String args[]) {
    
          /* This is how to declare HashMap */
          HashMap<Integer, String> hmap = new HashMap<Integer, String>();
    
          /*Adding elements to HashMap*/
          hmap.put(12, "Chaitanya");
          hmap.put(2, "Rahul");
          hmap.put(7, "Singh");
          hmap.put(49, "Ajeet");
          hmap.put(3, "Anuj");
    
          /* Display content using Iterator*/
          Set set = hmap.entrySet();
          Iterator iterator = set.iterator();
          while(iterator.hasNext()) {
             Map.Entry mentry = (Map.Entry)iterator.next();
             System.out.print("key is: "+ mentry.getKey() + " & Value is: ");
             System.out.println(mentry.getValue());
          }
    
          /* Get values based on key*/
          String var= hmap.get(2);
          System.out.println("Value at index 2 is: "+var);
    
          /* Remove values based on key*/
          hmap.remove(3);
          System.out.println("Map key and values after removal:");
          Set set2 = hmap.entrySet();
          Iterator iterator2 = set2.iterator();
          while(iterator2.hasNext()) {
              Map.Entry mentry2 = (Map.Entry)iterator2.next();
              System.out.print("Key is: "+mentry2.getKey() + " & Value is: ");
              System.out.println(mentry2.getValue());
           }
    
       }
    }

输出

key is: 49 & Value is: Ajeet
    key is: 2 & Value is: Rahul
    key is: 3 & Value is: Anuj
    key is: 7 & Value is: Singh
    key is: 12 & Value is: Chaitanya
    Value at index 2 is: Rahul
    Map key and values after removal:
    Key is: 49 & Value is: Ajeet
    Key is: 2 & Value is: Rahul
    Key is: 7 & Value is: Singh
    Key is: 12 & Value is: Chaitanya