java - Get the next sequence in an arithmetic or geometric progression -

i want make application takes sequence of 3 numbers per line produce , stops when reaches sequence of zeros , prints if it's arithmetic progression or geometric progression , next number in series.

example input:

4 7 10     2 6 18     0 0 0 

should output

ap 13     gp 54 

here code wanna know what's wrong , possibilities won't work code.

import java.io.bufferedreader; import java.io.ioexception; import java.io.inputstreamreader; public class main {     static string s="";     public static void main (string[] args) throws ioexception     {     string c;          string a[];         bufferedreader br = new bufferedreader(new inputstreamreader(system.in));         {             c= br.readline();             = c.split(" ");             if(c.charat(0)!='0'){             calc(a[1], a[2]);             }         }while((c.charat(0))!='0');         printer(s);     }     public static void calc(string a, string b){             int x = integer.parseint(a);             int y = integer.parseint(b);             if(y%x==0){                 s += "gp" +" " + (y*(y/x)) + "z";                 return;              }else{                 s += "ap" + " " + (y + (y-x)) + "z";                 return;             } }     public static void printer(string s){         string p= "";         for(int =0;i<=s.length()-1;i++){             if(s.charat(i)!='z'){                 p+= s.charat(i);             }else{                 system.out.println(p);                 p= "";             }         }     } } 

your problem discover progression type incorrectly. example, 0 4 8 ap, algorithm gp. example: 8 4 2 gp, 2%4 return false, saying ap. also, don't proceed cases when offered sequence not progression @ all.

it absolutely clear 3 numbers should involved. suppose integer numbers a, b, c form ap or gp, , need discover progression is. simple math can used:

1. if form ap, a + c = b + b. next element c + c - b
2. if form gp, a * c = b * b. next element c * c / b

(please notice how + changed *, , - /, when switch ap gp).