Is if(x) same as if(x==true)?

Question

Ok, so let's say I have an if statement and a boolean x:

if (x) {
    // some stuff
}

What happens here? Does this mean the same thing as if(x == true) ?

Solution 1

Yes,

if(x) {

}

is the succinct equivalent of

if(x == true) {

}

As @Sotirios points out, they are different at the bytecode level. Consider the following Java class:

class Test { 
   public void foo() { 
      boolean x = true;
      if(x == true) { 
      }
   }
}

emits:

  public void foo();
    Code:
       0: iconst_1      
       1: istore_1      
       2: iload_1       
       3: iconst_1      
       4: if_icmpne     7
       7: return 

vs

class Test { 
   public void foo() { 
      boolean x = true;
      if(x) { 
      }
   }
}

which emits:

  public void foo();
    Code:
       0: iconst_1      
       1: istore_1      
       2: iload_1       
       3: ifeq          6
       6: return  

I don't think this has any bearing on the performance or correctness of the program.

Solution 2

Yes, it is.

if checks if the condition is true, and if it is, executes the body statement. So x needs to be a boolean expression.

In fact x is equivalent to x == true if x is a boolean expression, so you should use x as it is more concise. This becomes clearer if the variable has a proper name for a boolean, e.g.

if (this.isVisible()) {
    this.hide();
}

vs.

if (this.isVisible() == true) {
    this.hide();
}

The first one is better to read.

Solution 3

Yes, it is same as if(x == true). In fact if(x) is recommended.

See the examples in The if-then and if-then-else Statements in The Java tutorial.

Solution 4

If x can be resolved as a boolean, and the value is "true", the "other stuff" will be executed.

Solution 5

Yes, it means the same thing as if you had if(x == true).

View more solutions

Comments

[Amir Afghani]

yes, yes it does.

[Freedom]

Okay thanks, I've been seeing a lot of this used in code and I was always wondering.

[Sotirios Delimanolis]

Semantically, it is equivalent. At the bytecode level, it is not.

[Kayaman]

@SotiriosDelimanolis Really? Any good reason the compiler doesn't compile it to the same bytecode?

[Sotirios Delimanolis]

@Kayaman Yes. As for a good reason, I don't know. The == is an extra operation.

[yitzih]

and at the other end if(!x) is the same as if(x != true) or if(x == false)

[david.pfx]

It means exactly the same, but whether the same code is generated depends on the compiler. It should be, but don't count on it.

[Raedwald]

See also stackoverflow.com/questions/7529344/…

[Mattias Buelens]

x ? true : false is just as redundant as x == true, and they're both equivalent to simply x.

[Admin]

Well i just wrote this example to make sure that he knows this version of an if statement too. It isn't a example for production.