CODEWITHSUNDEEP
javaif-statementwhile-loop
Matt Martin
Matt Martin

Reputation: 855

Java- why is if() block inside of while() statement executed?

I would need explanation, why is if() block inside of while() statement executed.It's said that: The while statement evaluates expression, which must return a boolean value. If the expression evaluates to true, the while statement executes the statement(s) in the while block. So please, take a look at this code:

class test{
static int x;

public static void main(String args[]){
    while(x!=5){
        x=x+1;
        if(x==5)
            System.out.println("I'm 5 now!");
    }
  }
}

Once variable x gains amout of 5, shouldn't be (x!=5) considered as false? So how can be if block executed? Basically it seems like it returns true boolean value for expression 5!=5.

Thank you for explanation!

Upvotes: 1

Views: 190

Answers (8)

MightyPork
MightyPork

Reputation: 18861

When you enter the loop's body and x == 4, it proceeds.

Then, you add 1 to the variable.

It's 5 now, so the if's condition is true!

Upvotes: 3

1'hafs
1'hafs

Reputation: 579

It enters the while loop while x=4 i.e, (4!=5 right??)

and x=x+1 is executed inside the while loop, so x=5; and the next line inside while loop is if(x==5) System.out.println("I'm 5 now!");

as value of x is 5 , the execution enters the if condition and we will get the output as "I'm 5 now!"

Upvotes: 2

Ruchira Gayan Ranaweera
Ruchira Gayan Ranaweera

Reputation: 35557

  while(x!=5){ // here maximum value accept as true is 4
        x=x+1; // now 4+1 and x =5
        if(x==5) //yes condition satisfied 
            System.out.println("I'm 5 now!"); //so out put will print 
    }

Upvotes: 2

Seelenvirtuose
Seelenvirtuose

Reputation: 20618

The expression x == 5 is evaluated to true, because x is changed inside the while loop.

When x equals 4 (which means x != 5 still evaluates to true), the next line (x = x + 1) results in x being 5.

Upvotes: 1

Hunter McMillen
Hunter McMillen

Reputation: 61510

While loops are known as pre-condition loops, meaning they check a condition before executing some block of statements.

So when x becomes 5 in the body of the loop, the last condition that was actually checked was x != 4.

x != 5 will be checked the next iteration of the loop.

Upvotes: 2

fge
fge

Reputation: 121720

When you enter the loop with X equal to 4, it is first incremented to take value 5, therefore satisfying the expression x == 5.

But then, at the next iteration, the condition in while is not true anymore.

Upvotes: 2

svz
svz

Reputation: 4588

This is because your x becomes equal to 5 after it enters the loop. On the next iteration the loop stops. You should move x=x+1 line after the if to make it work the way you want

Upvotes: 3

Tala
Tala

Reputation: 8928

If x == 4 then while is satisfied x != 5. Then you increment x x = x+1 and have x == 5. That's why

Upvotes: 5

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