[Java] 자바 이클립스 설치

HelloWorld

public class HelloWorldApp {
	public static void main(String[] args) {
		System.out.println("Hello World!!");
	}
}

HelloWorldApp은 HelloWorldApp.java 파일명과 동일

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Java의 동작원리

Java Source code.java
↓ compile
Java Application.class
↓
Java Virtual Machine
↓
computer

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Java로 데스크탑 앱 만들기

import javax.swing.*;   
import java.awt.Dimension;
import java.awt.Toolkit;
public class HelloWorldGUIApp{
    public static void main(String[] args){
        javax.swing.SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                JFrame frame = new JFrame("HelloWorld GUI");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setPreferredSize(new Dimension(800, 300));
                JLabel label = new JLabel("Hello World!!", SwingConstants.CENTER);
                frame.getContentPane().add(label);
                Dimension dim = Toolkit.getDefaultToolkit().getScreenSize();
                frame.setLocation(dim.width/2-400/2, dim.height/2-300/2);

                frame.pack();
                frame.setVisible(true);
            }
        });
    }
}