java - Generic class for operations on Number -

i writing java class represent range. make more general range can number type, 2 values v1 , v2, must in same number type.

although can comparison on them, cannot add or subtract values. know operation on 2 different number types cause problem (e.g. float + integer), , subclasses of number, e.g. biginteger , bigdecimal. in case, v1 , v2 should of same type.

class range<t extends number & comparable<t>> {     public t v1;     public t v2;     public range(t v1, t v2) {         if (v1.compareto(v2) > 0)             throw new illegalargumentexception("value-1 must smaller or equal value-2.");         this.v1 = v1;         this.v2 = v2;     }     public t length() {         return v2 - v1; // compilation error     } } 

recently come idea this:

public t add(t t1, t t2) {     if (t1 instanceof integer) {         // ...     }     if (t1 instanceof long) {         // ...     } }  

but there better design create range class? thanks!

make range , length() abstract. note v1 , v2 should protected.

abstract class range<t extends number & comparable<t>> {     protected t v1;     protected t v2;     public range(t v1, t v2) {         if (v1.compareto(v2) > 0)             throw new illegalargumentexception("value-1 must smaller or equal value-2.");         this.v1 = v1;         this.v2 = v2;     }      public abstract t length();  } 

extend range class specific types :

class integerrange extends range<integer> {      @override       public integer length() {           return v2 - v1;       }  } 

this in line open-closed principle. class should open extension, closed modification. using instanceof checks easiest way go against principle since range need modified each new type has support. should avoided in case.