I know that one of them is bitwise and the other is logical but I can not figure this out:
Scanner sc = new Scanner(System.in);
System.out.println("Enter ur integer");
int x=sc.nextInt();
if(x=0)//Error...it can not be converted from int to boolean
System.out.println("...");
The error means that x cannot be converted to boolean or the result of x=0 can not be converted to boolean.
== checks for equality. = is assignment.
What you're doing is:
if( x = Blah ) - in Java this statement is illegal as you can not test the state of an assignment statement. Specifically, Java does not treat assignment as a boolean operation, which is required in an if statement. This is in contrast with C/C++, which DOES allow you to treat assignment as a boolean operation, and can be the result of many hair-pulling bugs.
== is an equality check. if (x == 0) // if x equals 0
= is an assignment. x = 0; // the value of x is now 0
if(x=0)
Here you're assigning the value of 0 to the variable x. The if statement in Java can't evaluate an integer argument as it can in many other languages. In Java, if requires a boolean. Try
if(x == 0)
to do a comparison.
When you write 'x = 0' you are saying "Store 0 in the variable x". The return value on the whole expression is '0' (it's like this so you can say silly things like x = y = 0).
When you write 'x == 0' it says "Does x equal 0?". The return value on this expression is going to be either 'true' or 'false'.
In Java, you can't just say if(0) because if expects a true/false answer. So putting if(x = 0) is not correct, but if(x == 0) is fine.
Interpret the error to mean
"The expression
x=0
cannot be converted to Boolean."
As others have already said, '=' is assignment; '==' is compare.
in your program change
if(x=0)
to
if(x==0)
Just to clarify about C/C++ - assignment is evaluated to the right operand
if(a = n)
is evaluated to n, so (n = 1) is true (n = 0) is false
"==" checks for equality
"=" Is used for assignment.
It is giving you error cause you're assigning value to x in if(), where you're supposed to check for the equality. Try changing it to equality instead of assignment operator.
I know the question has been answered, but this still comes up from time to time not as a programmer error but as a typographical error (i.e., the programmer knew what he meant, but failed). It can be hard to see, since the two look so similar.
I've found that a way to help avoid doing this is to put the constant expression on the left-hand-side, like so:
if (0 == x)
...
That way, if I accidentally use only one "=" sign, the compiler will fail with an error about assigning to a constant expression, whether or not the assignment operator is left-associative and whether the if conditional expects a strongly-typed Boolean.
One interesting note: Since assignment operator evaluates to the right operand, the following is valid in Java(albeit not pretty):
if (( x = blah ) > 0) ...
Parenthesis are needed because of operator precedence ( '>' binds stronger than '=').