Validating jtextfield has input

Can someone kindly explain why this seemingly logical construction doesn't work?
if(txtOperand1.getText()==null)
JOptionPane.showMessageDialog(this,"nothing in op 1");
I'm just trying to make a simple calculator that needs to know that something has been entered into the operand fields.
Thanks!

Perhaps your test looked like this:if(txtOperand1.getText()=="")? If so, then that would explain why it didn't work. To compare the contents of two String objects you must use their equals() method, like this:if(txtOperand1.getText().equals(""))PC²

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