Thread: 2 questions(an error and line breakpoint?)

ok i made this and when i try to run it i get a compilation error and i have a question about something im seeing on eclipse

package wlodmgcalc;
 
import javax.swing.*;
import java.awt.*;
import java.awt.Event.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
 
public class wlocalc extends JFrame implements ActionListener, ItemListener {
 
	public wlocalc() {
		super("Dmg Calculator");
		setSize(200, 210);
		setBackground(Color.white);
		setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		FlowLayout flow = new FlowLayout(FlowLayout.LEFT);
		setLayout(flow);
 
		JPanel row1 = new JPanel();
		JLabel atkLabel = new JLabel("Attack:");
		row1.add(atkLabel);
		JTextField atk = new JTextField(7);
		row1.add(atk);
		add(row1);
 
		JPanel row2 = new JPanel();
		JLabel elementLabel = new JLabel("Element:");
		row2.add(elementLabel);
		String[] elements = { "Wind", "Fire", "Water", "Earth" };
		JComboBox elementBox = new JComboBox(elements);
		elementBox.setSelectedIndex(2);
		row2.add(elementBox);
		add(row2);
 
		JPanel row3 = new JPanel();
		FlowLayout flowbutton = new FlowLayout(FlowLayout.CENTER, 50, 10);
		row3.setLayout(flowbutton);
		JButton calculate = new JButton("Calculate");
		calculate.addActionListener(this);
		row3.add(calculate);
		add(row3);
 
		JPanel row4 = new JPanel();
		JLabel totalLabel = new JLabel("Damage: ");
		JTextField damageTotal = new JTextField(5);
		row4.add(totalLabel);
		row4.add(damageTotal);
		damageTotal.setEditable(false);
		add(row4);
 
		pack();
		setVisible(true);
 
		atk.addItemListener(this);
	}
 
	public void actionPerformed(ActionEvent event) {
		String atkNumber = atk.getActionCommand();
		String pressed = event.getActionCommand();
		if (pressed.equals("Calculate")) {
		System.out.println(atkNumber);	
		}
	}
 
	public static void main(String[] args) {
		wlocalc dmg = new wlocalc();
	}
}

the error i get is

Exception in thread "main" java.lang.Error: Unresolved compilation problem:

at wlodmgcalc.wlocalc.main(wlocalc.java:65)

and the other question i have is 1 line in eclipse has a little purple dot next to it and says
"Line Breakpoint:wlocalc [line:24] - wlocalc()"

no idea what that means and i dont see anything wrong with line 65 either so im pretty lost. any help is very much appreciated thanks

ill google the breakpoint and see what comes up

line 65 it says is

public static void main(String[] args) {

usually i get some errors or so but when i try to run thats what comes up and the program terminates and i have some markers showing but not sure how to fix them...im having trouble getting how to make a gui work with my program its not getting through my thick skull lol

weird i dont see any of that one mine usually i get red X or so on the left side with errors but none there now lol

the linebreak i found was cause i went into debug mode to try it out and i guess the program stopped there but i toggled it off maybe thats why im having so much problems with it

when i tried on command line i got an "is not recognized as an internal or external command operable program or batch file" and it wouldnt do anything

ah thank you that explains the first error i guess ill stop using the * too and save some hassle thanks a lot

im checking the path out right now hopefully i just made some mistake in the path or so

In my experience, clashes don't happen very often, and when they do (e.g. you need to use both classes, or as in the case above), you just have to explicitly qualify one class (usually the one you use least). With wildcard imports, you can add an explicit import for the clashing type you actually use (or use most often if you use both), and explicitly qualify the clashing type you use least. The compiler warns you when there's an unresolved name clash, so it's no problem.

For example, if you use java.util.Date more in the code than java.sql.date, you could do this:

import java.sql.*;
import java.util.*;
import java.util.Date; // explicitly import the class you use (or use most often) when there's a name clash.
 
class NoProblem {
    Date d;                 // by default will use java.util.Date because of explicit import
    java.sql.Date s;      // to use java.sql.Date you need to explicitly specify its package
}

Of course, this is only needed when you're using many classes from a single package and there's a name clash with another package, and you want to avoid a rash of unnecessary import statements. The explicit import of one class and the explicit qualification of the other make it pretty clear which is which in the code.

Most decent IDEs will have a setting where you can specify the number of separate imports from a single package at which the separate import statements will replaced by a single wildcard import. Wildcard imports are optional, but they're provided for a good reason.