Java- double variable issue -

here's simple equations counter.now counts equations 2 variables.it's based on trying many combinations (4 milion or 16 milion) of a , b variables.so code works , counts exact.but since tried change variable b double, things go wrong.i've expected line b=b+0.1 secures setting variable b each 10th time 1.0.but imidiately after start way more decimal numbers appear each b.so use wrong datatype? or should raise variable b different value?(i tried changing variables double).thank suggestions!

import java.io.bufferedreader; import java.io.ioexception; import java.io.inputstreamreader;  public class buffer{ static int a; static double b; static bufferedreader reader; static string query; static int range; static int result;  public static void main(string[] args)throws ioexception{     reader=new bufferedreader(new inputstreamreader(system.in));      system.out.print("choose speed of test(fast or slow):");     query=reader.readline();      if(query.equals("fast"))         range=2000;     else         range=4000;       //start test//            while((a+b)!=26000){         b=b+0.1;         if(b==range+1){             b=0;             a=a+1;         }         if((a+b)!=26000)             system.out.println("a- "+a+", "+"b- "+b+"=false.");          if((a+b)==26000){             system.out.println("a- "+a+", "+"b- "+b+"=true.");             system.out.println("\n"+"done.you can possibly solve equation, if a= "+a+" , b= "+b+".");         }         if(a==range&&b==range&&(a+b)!=26000){             system.out.println("\n"+"tested "+a*b+" options.solution not found.");             system.exit(0);         }     }    } } 

you can use bigdecimal instead of float/double primitives avoid issues. of described here: java mistake 1 - using float , double monetary or financial calculation