java - How to write hashCode method for a particular class? -

i'm trying generate hashcode() method simple class i'm not getting anywhere it. appreciate help. i've implemented equals() method, looks follows, , know if need implement compareto() method. i've imported java.lang.character use character.hashcode() doesn't seem work.

private class coord{     private char row;     private char col;     public coord(char x, char y){         row = x;         col = y;     }     public coord(){};      public char getx(){         return row;     }      public char gety(){         return col;     }      public boolean equals(object copy){         if(copy == null){             throw new nullpointerexception("object entered empty");         }         else if(copy.getclass()!=this.getclass()){             throw new illegalargumentexception("object entered not coord");         }         else{             coord copy2 = (coord)copy;             if(copy2.row==this.row && copy2.col==this.col)                 return true;             else                 return false;         }     }  } 

thanks in advance...

the comparto() method giving me java.lang.comparable casting error..

public int compareto(object copy){         if(copy==null){             throw new nullpointerexception("object entered empty");         }         else if(copy.getclass()!=this.getclass()){             throw new illegalargumentexception("object entered not coord");         }         else{             coord copy2 = (coord)copy;             if(copy2.row==this.row && copy2.col==this.col){                 return 0;             }             else if(copy2.col < this.col){                 return -1;             }             else{                 return 1;             }         }     } 

thanks...

to implement hashcode, override default implementation object:

@override public int hashcode() {     return row ^ col; } 

this isn't ideal hash, since results predictable , easy 2 different coord objects return same value. better hash make use of built-in arrays class java.util (http://docs.oracle.com/javase/7/docs/api/java/util/arrays.html):

@override public int hashcode() {     return arrays.hashcode(new object[]{new character(row), new character(col)}); } 

you can use method generate pretty hash number of fields.

to implement compareto, you'll want class implement comparable:

public class coord implements comparable<coord> 

once you've done this, can make compareto take argument of type coord rather type object, save trouble of checking type.