Java String Comparison

Question

The following code is a part of my program

    String [] currency = { "Euro" , "USD" , "Pound" };
private JComboBox
C1 = new JComboBox(currency),
C2 = new JComboBox(currency);
String s,r;
double i,j =0,k=0;

................

private ActionListener d = new ActionListener() {
public void actionPerformed(ActionEvent e) {
Object obj = C2.getSelectedItem();

r = "" + obj;
st.setText(r);
System.out.println(r);
System.out.println(currency[0]);

if (r == currency[0])
{

k=1;
}

if (r == currency[1])
{
k = 1.161;
}

if (r == currency[2])
{
k= 0.954;
}
System.out.println(k);
}
};

when r is printed the output is good same case for the printing of currency[0]. The problem is that k is always seen as 0.00. I think it has to do with the comparison of the strings.

Thanks.

Answer 1

Use equals for string comparison Eg, "string".equals("other string"); or in your case

r.equals(currency[0])

When using == on objects you are only comparing references (ie, memory location, not actual content equality).

You might also be interested in using Enums for your currency sample.

Answer 2

compare the two strings by

r.equals(currency[0])

or

r.equalsIgnoreCase(currency[0])

when you don't care about the case of the characters (uppercase or lowercase)

Answer 3

You should use equals for string comparison, and remember to put the string that is not null first:

"Hello".equals(myString)

or in your case:

r.equals(currency[0])