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Groups > comp.lang.java.programmer > #39123

Re: Best way to make a hashcode?

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On Monday, August 26, 2019 at 7:04:02 PM UTC-4, Arne Vajhøj wrote:
> 
> Have tried letting your IDE generate hashCode and equals based
> on the fields you want?
> 
> Arne

Didn't realize it could do that...so here's what it comes up with.


import java.util.HashMap;

public class TestClass1 {
     String s1 = "abc";
     String s2 = "def";
     String s3 = "ghi";
     int x = 1;
     int y = 2;
     float z = 3;

     @Override
     public int hashCode() {
          final int prime = 31;
          int result = 1;
          result = prime * result + ((s1 == null) ? 0 : s1.hashCode());
          result = prime * result + ((s2 == null) ? 0 : s2.hashCode());
          result = prime * result + ((s3 == null) ? 0 : s3.hashCode());
          result = prime * result + x;
          result = prime * result + y;
          result = prime * result + Float.floatToIntBits(z);
          return result;
     }

     @Override
     public boolean equals(Object obj) {
          if (this == obj) return true;
          if (obj == null) return false;
          if (getClass() != obj.getClass()) return false;
          TestClass1 other = (TestClass1) obj;
          if (s1 == null) {
               if (other.s1 != null) return false;
          } else if (!s1.equals(other.s1)) return false;
          if (s2 == null) {
               if (other.s2 != null) return false;
          } else if (!s2.equals(other.s2)) return false;
          if (s3 == null) {
               if (other.s3 != null) return false;
          } else if (!s3.equals(other.s3)) return false;
          if (x != other.x) return false;
          if (y != other.y) return false;
          if (Float.floatToIntBits(z) != Float.floatToIntBits(other.z)) return false;
          return true;
     }

     public static void main(String[] args) {
          TestClass1 c1 = new TestClass1();
          TestClass1 c2 = new TestClass1();
          HashMap<TestClass1,String> m1 = new HashMap<>();
          m1.put(c1, "test");
          System.out.println(m1.containsKey(c2)); //true
     }

}

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Thread

Best way to make a hashcode? Eric Douglas <e.d.programmer@gmail.com> - 2019-08-26 13:51 -0700
  Re: Best way to make a hashcode? Eric Sosman <esosman@comcast-dot-net.invalid> - 2019-08-26 17:41 -0400
    Re: Best way to make a hashcode? Eric Douglas <e.d.programmer@gmail.com> - 2019-08-27 06:24 -0700
      Re: Best way to make a hashcode? Eric Sosman <esosman@comcast-dot-net.invalid> - 2019-08-27 09:39 -0400
        Re: Best way to make a hashcode? Eric Douglas <e.d.programmer@gmail.com> - 2019-08-27 07:29 -0700
          Re: Best way to make a hashcode? Eric Sosman <esosman@comcast-dot-net.invalid> - 2019-08-27 11:49 -0400
            Re: Best way to make a hashcode? Eric Douglas <e.d.programmer@gmail.com> - 2019-08-27 11:05 -0700
              Re: Best way to make a hashcode? Eric Sosman <esosman@comcast-dot-net.invalid> - 2019-08-27 15:16 -0400
                Re: Best way to make a hashcode? Eric Douglas <e.d.programmer@gmail.com> - 2019-08-27 13:04 -0700
                Re: Best way to make a hashcode? Daniele Futtorovic <da.futt.news@laposte-dot-net.invalid> - 2019-08-27 23:51 +0200
    Re: Best way to make a hashcode? Silvio <silvio@internet.com> - 2019-08-28 01:27 +0200
      Re: Best way to make a hashcode? Marcel Mueller <news.5.maazl@spamgourmet.org> - 2019-09-06 19:42 +0200
  Re: Best way to make a hashcode? Arne Vajhøj <arne@vajhoej.dk> - 2019-08-26 19:03 -0400
    Re: Best way to make a hashcode? Eric Douglas <e.d.programmer@gmail.com> - 2019-08-27 04:59 -0700
      Re: Best way to make a hashcode? Arne Vajhøj <arne@vajhoej.dk> - 2019-08-27 21:08 -0400
        Re: Best way to make a hashcode? ross.finlayson@gmail.com - 2019-09-05 20:27 -0700
  Re: Best way to make a hashcode? trisha guillot <guillottrisha347@gmail.com> - 2020-01-18 07:25 -0800

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