is checking a boolean faster than setting a boolean in java?

Question

This:

if (var) {
    var = false;
}

Versus this:

var = false;

Is there a speed difference?

Answer 1

The first code contains a comparison, so your compiler maybe generate a java bytecode that looks like:

  public static void main(java.lang.String[]);
    Code:
       0: iconst_1      
       1: istore_1      
       2: iload_1       
       3: ifeq          8
       6: iconst_0      
       7: istore_1      
       8: return    

For the second code the generated bytecode is shorter because the comparison is missing:

  public static void main(java.lang.String[]);
    Code:
       0: iconst_1      
       1: istore_1      
       2: iconst_0      
       3: istore_1      
       4: return      

The virtual machine needs more time for executing 8 commands in the first example than 4 commands in the second one. Although this difference should not be to high the second code is more clearly.

Put your code in a simple main method and compile the class. Then run a command prompt and change to java/bin directory. To disassemble your class call javap -c path/to/YourClass.class >> path/to/bytecode.txt. bytecode.txt will contain the java bytecode of your class.