Variables not changing on action.

So i'm new to java and for one of our assignments we have to make an application that can either calculate the area of a triangle, or volume of a box. Everything in my code works but only if I change variables within the code itself, ill post the important bits and hopefully I can get some of your input.

Code Java:

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public class Week05 {
	boolean tri;
        private void initialize() {
             btnTriangle.addActionListener(new ActionListener() {
			public void actionPerformed(ActionEvent e) {
				tri = true;
				lblTitle.setText("Area of Triangle");
				btnTriangle.setEnabled(false);
				btnBox.setEnabled(true);
				lblA.setText("Enter S1");
				lblB.setText("Enter S2");
				lblC.setText("Enter S3");
				txtA.setEditable(true);
				txtB.setEditable(true);
				txtC.setEditable(true);
			}
		});
		btnTriangle.setBounds(70, 45, 89, 23);
		frame.getContentPane().add(btnTriangle);
 
		btnBox.addActionListener(new ActionListener() {
			public void actionPerformed(ActionEvent e) {
				tri = false;
				lblTitle.setText("Volume of a Box");
				btnBox.setEnabled(false);
				btnTriangle.setEnabled(true);
				lblA.setText("Enter l");
				lblB.setText("Enter w");
				lblC.setText("Enter h");
				txtA.setEditable(true);
				txtB.setEditable(true);
				txtC.setEditable(true);
			}
		JButton btnNewButton = new JButton("Calculate");
		btnNewButton.addActionListener(new ActionListener() {
			public void actionPerformed(ActionEvent e) {
				double a, b, c;
				a = Double.parseDouble(txtA.getText());
				b = Double.parseDouble(txtB.getText());
				c = Double.parseDouble(txtC.getText());
				while ( a <= 0 || b <= 0 || c <= 0){
					txtOutput.setText("Values are less than 0");
					return;
				}
				if(tri = true){
					Triangle area = new Triangle( a, b, c);
					txtOutput.setText("The area of the Triangle is" + area.getArea());
				}
				else if(tri = false) {
					Box volume = new Box( a, b, c);
					txtOutput.setText("The volume of the Box is" + volume.getVolume());
				}
			}
		});

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the problem I seem to be having is that my variable tri never changes to false, or if I switch boolean expressions it never changes true on the action of pressing the button for triangle or box.

Does this even compile? I see a lot of problems that the compiler *should* complain about.
But your problem is with this statement:

Code java:

---

if(tri = true){...
}
else if(tri = false)...

---

A single-equals is an assignment, a double-equals is a comparison. So you need this instead:

Code java:

---

if(tri == true){...
}
else if(tri == false)...

---

If statements look for conditionals (binary results of either true or false), and a boolean is a conditional, so this is also acceptable:

Code java:

---

if(tri) {...
}
else if(!tri)...

---

this was only part of the code that was giving me grief in the application. i actually saw that about a half an hour of staring at it, the == was my only problem and thanks anyways.