java - Else condition seemingly fails to execute -

i creating simple mathematics practice program, running serious issue else conditions. when conditions should trigger else block run, if statement runs instead, ie if program prompts user answer question 7+6, if input 5 still procede if had input proper answer. have combed through each iteration of if else series (this 1 of 5) last few hours, cannot figure occurring prevent else segment running.

correctrange / correctrange2 random generated int values (currently 7 & 6 respectively d1 & d2 same values doubles human error parameter when input1 = q program supposed end edit: here updated version, error persists

  //addition         boolean addition = false; while(input1 == 'a'|| input1 == 'a') {     system.out.println("what solution problem " + correctrange              + " + " +  correctrange2 );     double input2 = userinput.nextdouble();     if(input2 <= (d1 + d2) + human ||         input2 >= (d1 + d2) - human)     {system.out.println("that correct!");      system.out.println("what practice next?");      addition = true;     }     while (!addition)      {system.out.println("the correct solution " +                 correctrange + correctrange2);         input1 = 'q';         }     input1 = userinput.next().charat(0); } 

every time call userinput.nextdouble() reads new double. if call twice expect new double.

if(userinput.nextdouble() <= (d1 + d2) + human ||     userinput.nextdouble() >= (d1 + d2) - human) 

this read 1 or 2 double if first condition false.

most intended

double input = userinput.nextdouble(); if(input <= (d1 + d2) + human ||     input >= (d1 + d2) - human) 

or can write

if(math.abs(input - (d1 + d2)) <= human) 

note: = assignment , == comparison so

while (addition = false)  

is false intended be

while (addition == false)  

or better

while (!addition)