If a is 0 , then equation is not quadratic , but linear
if ( a == 0 ) { System . out . println ( " Invalid " ) ; return ; } int d = b * b - 4 * a * c ; double sqrt_val = sqrt ( abs ( d ) ) ; if ( d > 0 ) { System . out . println ( "Roots are real and different NEW_LINE"); System . out . println ( ( double ) ( - b + sqrt_val ) / ( 2 * a ) + "NEW_LINE" + ( double ) ( - b - sqrt_val ) / ( 2 * a ) ) ; } else if ( d == 0 ) { System . out . println ( "Roots are real and same NEW_LINE"); System . out . println ( - ( double ) b / ( 2 * a ) + "NEW_LINE" + - ( double ) b / ( 2 * a ) ) ; }