I wonder why first code output is 000 while the second one is 123
first one:
int z=0;
while(z<4)
{
z=z++;
System.out.print(z);
}
second one :
int z=0;
int x=0;
while(z<5)
{
x=z++;
System.out.print(x);
}
what is the different between these two codes , why the first block do not increase the value of the z ?
When you use the post-increment operator, you don't need to assign the result back to the variable.
That is, your code should look like this:
int z=0;
while(z<4)
{
++z;
System.out.print(z);
}
In Java, the operation returns the value of z BEFORE the increment (while incrementing the variable behind the scenes afterwards), and that value is then RE-assigned to z. That's why it never changes.
The pre-increment operator will do the increment and return the NEW result, so you'll get what you expect:
int z=0;
while(z<4)
{
z=++z;
System.out.print(z);
}
This will print 1234.
It's because you are assigning the value of z with a postfix operator.
http://download.oracle.com/javase/tutorial/java/nutsandbolts/operators.html
int z = 0;
i = z++; // i equals 0
x = ++z; // x equals 2
Postfix operators will increment the value of z after assignment of i.
Unary operator ++ will increment the value of z before assignment of x.
Think of it as ++ before z as +1 before assignment, ++ after z as +1 after assignment.