while vs. if

[Manish Agarwal]

hi all
when i use while(false) in the code i got an error message saying
Unreachable code.But if i use if(false) i do not get an error.Why?
please explain.
Thanx.

class Testing{
public static void main(String[] args) {
while(false){
System.out.println("Hello World!");
}
        }
}  

[n.chenththuran]

hi,
while loop functions for (true) conditions. if u give false the rest of the code inside loop cant be reached

[n.chenththuran]

check this


while(true){
System.out.println("hi world");
}


a non ending loop

[Corey McGlone]

This was really implemented to allow the use of development-time checks that could be easily removed when a system went to production. For example, you could write code that looked like this:

public class SomeClass
{
    public static boolean IN_PRODUCTION = false;
 
    public static void main(String[] args)
    {
        // Some code
 
        if ( !IN_PRODUCTION )
        {
            // Some code
        }
    }
}

When the system went to production, you could easily change the single line to set the variable IN_PRODUCTION to true and all of your development debugging code would automatically cease executing.

Obviously, you'd never use a while statement for this type of work, so it was only necessary to make if(false) compile - while(false) could still generate a compiler error.

Today, there is no need to do this. With Java 1.4, you have the capability to use assertions to do this exact type of thing for you.

[Manish Agarwal]

thanks for all for immediate reply.

[Murtuza Akhtari]

Read the explanation in the JLS ....After reading this question put up by Manish, I checked the JLS and found this out...as to why they have implemented it that way !!
Read the last part where you see the word 'HYPOTHETICAL' (Its a long document so you would have to scroll down quite a bit)

JLS