content: import java.util.HashMap;
  import java.util.HashSet;
  
  public class Main {
  
      public static void main(String[] args) {
  
          int a = 20;
  
          int b = -20;
          /**
           * 20
           * -20
           * **/
          System.out.println(((Integer)a).hashCode());
          System.out.println(((Integer)b).hashCode());
  
          double c = 3.1415926;
  
          /**
           * 219937201
           * **/
          System.out.println(((Double)c).hashCode());
  
          String d = "ilovejwl";
  
          /**
           * -1332433020
           * **/
          System.out.println(d.hashCode());
  
          Student jwl = new Student(10,4, "wenli", "jia");
  
          /**
           * -791031681
           * **/
          System.out.println(jwl.hashCode());
  
          HashSet<Student> set = new HashSet<>();
          set.add(jwl);
  
          HashMap<Student, Integer> scores = new HashMap<>();
          scores.put(jwl, 100);
  
          Student jwl2 = new Student(10,4, "wenli", "jia");
          /**
           * -791031681
           * **/
          System.out.println(jwl2.hashCode());
      }
  }
  