Increament Operator Error

[himanshu124]

i started learning JAVA a few days back.
i thought of writing my first program on arithmetic operators.
but i m getting compilation error with the "++" operator.
below is my code.

public class IntArithmeticOperations {
       public static void main(String args[]){
	 System.out.println("Arithmetic Operations Sample");
	 
	 int i=10;
	 
	 int increamentResult=++i;//This is ok
	 int increamentResult1=++(i);//This is also ok
	 int increamentResult2=doit(++i);  //This is also ok
	 int increamentResult3=++(++i);   //This gives a compilation error
	 int increamentResult4=++(i=i++); //This gives a compilation error
	 int increamentResult5=++(i+1); //This gives a compilation error
	 
	 System.out.println("IncreamentResult is"+increamentResult);
	 System.out.println("IncreamentResult1 is"+increamentResult1);
	 System.out.println("IncreamentResult2 is"+increamentResult2);
	 System.out.println("IncreamentResult3 is"+increamentResult3);
	 System.out.println("IncreamentResult4 is"+increamentResult4);
	 System.out.println("IncreamentResult5 is"+increamentResult5);
    }
 public static int doit(int i){
	 return i;
 }
}

Please help me understand how the "++" operator works.

[wsaryada]

The ++ operators works with a variable and doesn't not with a value. For example the ++(i) works because i is a variable. But ++(++i) doesn't work because (++i) is a value and not a variable. The compiler error message might already tell you that it "required a variable but found a value instead".

[himanshu124]

Thanks a lot this was bugging me since morning.

But still have a silly question isn't the expression "i++" evaluated by the compiler as "i=i+1".
so the in the instruction int increamentResult=++(i++) the expression in () be evaluated as i=i+1 and the instruction be changed to int increamentResult=++(i) with the "i" in () having the new value?

sorry for my English.

[wsaryada]

Maybe the following example makes it clearer regarding variable or value.

1. variable means something like this:

int i = 10;
int j = ++i; // this works

2. value means something like this:

int j = ++10; // this will not work

The value of expression ++i and i = i + 1 is equals. but still ++i return the value of i incremented by 1. it is not the variable i.

[himanshu124]

Thanks this cleared all my doubts about ++ operator.

[pbrockway2]

i started learning JAVA a few days back.

int increamentResult4=++(i=i++);

Just my 2c, but this is not good Java to be learning.

Not because the line fails to compile, but, rather, because by some mischance it might compile: and mean g0d knows what.

[edit] Reading this again, this I should add... Welcome to the forums! And there's nothing wrong with asking about code like this.

In fact examining such monstrosities is a good way of getting understanding about the darker corners of the language. It's just that I don't think it a good place to start and that even if it was good (valid) Java, it would be bad (unclear) Java.

[himanshu124]

Just my 2c, but this is not good Java to be learning.

Not because the line fails to compile, but, rather, because by some mischance it might compile: and mean g0d knows what.

[edit] Reading this again, this I should add... Welcome to the forums! And there's nothing wrong with asking about code like this.

In fact examining such monstrosities is a good way of getting understanding about the darker corners of the language. It's just that I don't think it a good place to start and that even if it was good (valid) Java, it would be bad (unclear) Java.

Thanx pbrockway2. Will keep your advice in mind. Its just tat i come from a C background so had this weird curiosity of trying such a code ;)