Java Boolean wrong answer

Question

Hello I have got a little "problem" ... I just seems weird to me that when you check the code below that it says false if I type same number twice in the dialog fields.

I am kinda new to Java but not to programming itself and it does not make any sense.

Thanks in advance

    import javax.swing.*;


public class Praeinkrement {

    public static void main(String[] args) {

        String a = JOptionPane.showInputDialog("Zahl a");
        String b = JOptionPane.showInputDialog("Zahl b");


        Double c = Double.parseDouble(a);
        Double d = Double.parseDouble(b);

        boolean e, f;
        e = (c == d);
        f = (c < d);

        JOptionPane.showMessageDialog(null, e + "\n" + f);

    }
}

It does make sense. Read the linked duplicate, it explains the effect. In short: `==` compares for **identity** and not for *content*. Use the `equals` method if you want to compare for *content*. — Zabuzard, May 08 '18 at 10:53
@FelixPutzenlechner The same applies here. You need to use `.equals()` for comparing wrapper classes for equality. — Ivar, May 08 '18 at 10:58
or don't use boxed primitives unless the value can actually be null - and `parseDouble` never returns null. — Jaroslaw Pawlak, May 08 '18 at 11:00
See also https://stackoverflow.com/questions/13387742/compare-two-objects-with-equals-and-operator — Seelenvirtuose, May 08 '18 at 11:01

score 0 · Answer 1 · answered May 08 '18 at 10:55

0

Use .equals for value checking,

public static void main(String[] args) {

          String a = JOptionPane.showInputDialog("Zahl a");
            String b = JOptionPane.showInputDialog("Zahl b");

            boolean c = (a.equals(b));

            JOptionPane.showMessageDialog(null, c);
    }

answered May 08 '18 at 10:55

Balasubramanian

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No need to answer a question that already got marked as a duplicate! – Seelenvirtuose May 08 '18 at 10:59
initial itself answered. ok thanks. – Balasubramanian May 08 '18 at 11:01

Java Boolean wrong answer

1 Answers1