java - Why is there a "deadbranch" in my code? -

below code working fine until last if-else. appears i've done wrong boolean variables cangraduate , onprobation. perhaps i'm reassigning them incorrectly in prior if-else statements. deadbranch occurs @ else half of last if-else.

package lab5; import java.util.scanner; public class lab5 {  public static void main(string[] args) {      //creates scanner object     scanner scanner = new scanner(system.in);      //part ii     //creating variables     double gpa;     int totalcreditstaken;     int mathsciencecredits;     int liberalartscredits;     int electivecredits;     boolean cangraduate = true;     boolean onprobation = false;      //prompts user imput     system.out.println("what gpa?");         gpa = scanner.nextdouble();     system.out.println("what's total amount of credits you've taken?");         totalcreditstaken = scanner.nextint();     system.out.println("how many math , science credits have taken?");         mathsciencecredits = scanner.nextint();     system.out.println("how many liberal arts credits have taken?");         liberalartscredits = scanner.nextint();     system.out.println("how many elective credits have taken?");         electivecredits = scanner.nextint();      //creates first "if" statment determine if gpa high enough on track or on probation      if (gpa < 2.0){         system.out.println("you're on academic probation.");         onprobation = true;     }      //part iii     //creates conditional see if there's enough credits graduate      if (totalcreditstaken < 40 ){         system.out.println("you need more credit(s) graduate.");         cangraduate = false;     }     else{         system.out.println("examining credit breakdown...");         cangraduate = true;     }      //part vi     //nested if-else if-else determine if student qualifies ba or bs     if ((mathsciencecredits >= 9) && (electivecredits >= 10)){         system.out.println("you qualify bs degree.");         cangraduate = true;     }     else if ((liberalartscredits >= 9) && (electivecredits >= 10)){         system.out.println("you qualify ba degree.");         cangraduate = true;     }     else{         system.out.println("you don't meet degree requirments.");         cangraduate = false;     }      //part v     //uses if statement either congradulate student or tell student take more classes     if ((onprobation = true) || (cangraduate = false)){         system.out.println("you don't qualify graduate.");     }     else{         system.out.println("congradualations qualify graduate.");     }  } } 

a bit more explanation what's happening here.

in java, = operator assignment, not comparison (the comparison operator ==). if a int, a = 3 means "put value 3 in variable a".

but assignment expression. in addition putting value in variable, expression evaluates value assigned.

so value of expression a = 3 3. can things like:

system.out.println( = 3 ); 

this both put 3 in a, , print 3 on console.

usually, java doesn't allow confuse between = , ==. if variable int or float or string, writing statement like:

if ( = 3 ) ... // compilation error 

will not work because value of expression 3, int value, , if expects expression of type boolean. tell expression wrong, , you'll notice: "oh, meant ==".

but if type of a boolean, writing a = false or a = true assignment, returns value assigned - boolean. because of that, can write

if ( = false ) ... // compiles correctly 

and compiler won't complain, because value of expression boolean , that's if expects. compiler doesn't know meant compare. knows got expression of appropriate type.

for reason recommended never compare boolean variables @ all. instead of

if ( == true ) 

it correct write

if ( ) 

because if succeed when a true , fail when a false. no need compare! it's important give variable name did - cangraduate name, , statement like

if ( cangraduate ) 

is nicely readable "if [the user] can graduate...".

for false, can use

if ( ! cangraduate ) 

it's not nice-sounding in english, it's clear enough, , clearer if ( cangraduate == false ), added bonus not miss = , write if ( cangraduate = false ) mistake.