Use bitwise operator to create hash code : Bitwise Operators « Operators « Java Tutorial

1. Java Tutorial
2. Operators
3. Bitwise Operators

public class Main {
  int instanceField;
  {
    int hc = hashCode();
    instanceField = hc;
    for (int i = 0; i < 32; i++) {
      System.out.print((hc & 0x80000000) != 0 ? '1' : '0');
      hc <<= 1;
    }
  }

  public static void main(String[] args) {
    System.out.println(new Main().instanceField);
    System.out.println(new Main().instanceField);
  }
}