Why is my if statement executing when its false

[ProPatto16]

quick question, not sure why i can't work this out.
in the following code my if statement executes, but as far as i can see i have set the boolean so that it shouldnt.

public void actionPerformed(ActionEvent e)
               {
                   boolean contains = false; 
                   for (int i = 0; i < studentStrings.size(); i++)
                    {
                        if( studentStrings.get(i).contains( enterID.getText()))
                        {
                            System.out.println( " get constains executed");
                            contains = true;
                        }
                    }
                    if ( contains = true)
                    {
                        updateOldRecord();
                        System.out.println( "if executed");
                    }
                    else
                    {
                        newRecord();
                        System.out.println( "else executed");
                    }

you can see there are 2 ifs and one else. When and if the first one executes it should set the boolean contains to true. then if boolean contains is true my second if should execute and not my else. and if the first if doesn't execute the boolean should still be false so my else will execute. the system.print methods are just so i can see which ones are executing.

in the for statement the idea is i look for a string in the arrayList that is entered into a student ID text field. if the ID already exists it updates that student, if not it creates a new record.

the problem is whether or not that first if statement executes, only my second if executes, never the else.

so if my jtextfield has an existing ID number executed i get

get contains executed
if executed

and if it does not contain an existing ID then boolean should remain false and then only execute the else but i get

if executed.


i don't know why my if statement arguments arent working?

thanks

 

[gabbagabbahey]

You are missing an equals sign. If (contains = true) sets contains equal to true and then tests whether it is true. If (contains == true) just tests whether contains is true without changing its value.

 

[MisterX]

There is a difference between assignment and comparison.

The expression of assigning a boolean can be treated as a boolean.

boolean b = false;

if( b = true) //expression in () sets b to true and evaluates to true
{
    System.out.println( "THIS LINE WOULD GET PRINTED");
}

As an aside, one may write

if(b == true)

more concisely as

if(b)

 

[ProPatto16]

Thanks, knew it would be simple!

 

[rezeew]

I would suggest checking the logic of your if statement. In the code provided, the if statement is using the assignment operator (=) instead of the equality operator (==). This means that the statement will always evaluate to true, regardless of the value of the boolean variable contains. To fix this, you should use the equality operator in your if statement, as follows:

if (contains == true)

Additionally, you may want to consider using the contains() method directly on the ArrayList instead of iterating through it in a for loop. This could simplify your code and potentially avoid any logic errors.