I don't think you can use default argument values in Java but you can use overloading to achieve a similar effect.
ie.
Code:
public int myMethod ()
{
return 0*2;
}
public int myMethod (int a, int b)
{
return a*b;
}
public int myMethod (int x, boolean isA)
{
if (isA)
return x * 2;
else
return 0; // 0 * x
}