if statement doesn't check the condition

Question

Here is my problem, the if statement doesn't show the messagedialog when i don't insert anything in the inputdialog, but when i use != to compare the condition, it showup, why is this? as i know != mean not equal and == is equal

    String firstName = "";
    String lastName = "";

    firstName = JOptionPane.showInputDialog("Please enter your first name");

    if (firstName == "") {
        JOptionPane.showMessageDialog(null, "Don't leave it blank!");
    } else
    {
        lastName = JOptionPane.showInputDialog("Please enter your last name");
    }

    String msg = "Hello " + firstName + lastName + "!";
    JOptionPane.showMessageDialog(null, msg);

Yep, you're right -- Java's obviously broken. Has noting to do with attempting to compare strings with `==`. — Hot Licks, May 01 '13 at 03:33

score 3 · Accepted Answer · answered May 01 '13 at 03:33

3

One of the most common mistakes in java. String require a .equals() rather than an ==.

Wrong:

if (str == "foo") {

}

Right:

if ("foo".equals(str)) { // done in this order to avoid NPE

}

answered May 01 '13 at 03:33

nook

2,378
5
34
54

Then accept this answer, and we are all done here :D – nook May 01 '13 at 03:38
still 4 minute to accept the answer, dunno why :( – PotterWare May 01 '13 at 03:41
I think there is some time restraint on accepting, couldn't tell you why. But do it when you can, and happy coding mate :D. – nook May 01 '13 at 03:44

if statement doesn't check the condition

1 Answers1