JAVA Notes ​

public class <Class_name> { 
    public static void main(String[] args) {
         
    }
}

if (判斷式){
    // do something;
} else {
    // do something;
}

變數 = 判斷式 ? 成立回傳結果 : 不成立回傳結果 ;

for (設定初值 ; 判斷式 ; 設定增減量){
    // do something;
}

while (判斷式){
    // do something;
}

do {
    // do something;
} while (判斷式);

switch (變數) {
    case 1:
        // do something;
        break;
    case 2:
        // do something;
        break;
    case 3:
    case 4:
        // do somethings;
        break;
    default:
        // do something;
}

public static 型態 函式名稱 ( 參數型態 參數名稱 ){
    // do something;
    return 回傳值 ( 運算式 );
}

class Circle {
    double pi = 3.14;
    double radius;
    
    void printArea() {
        System.out.println("area = "" + pi * radius * radius);
    }
}

public class Main {
    public static void main (String args[]){
        Circle cir = new Circle();
        cir.radius = 5.0;
        cir.printArea();
    }
}

class Circle {
    private double pi = 3.14;
    private double radius;
    
    void printArea() {
        System.out.println("area = " + pi * radius * radius);
    }
    
    void setRadius(double r){
        radius = r;
    }
}

public class Main {
    public static void main (String args[]){
        Circle cir = new Circle();
        cir.setRadius(5.0);
        cir.printArea();
    }
}

import <package>.<class>;

public class Human{
	String name;
	int age;
	int height;
    
	private Human(){
	}
    
	public Human(String str){
        this.name = str;
	}
    
	public Human(String str, int a, int b){
        this.name = str;
        this.age = a;
        this.height = b;
	}
}

public class CallHuman{
    public static void main (String[] args){
        Human h1 = new Human();
        Human h2 = new Human("名稱");
        Human h3 = new Human("名稱", 數字a, 數字b);
    }
}

class Father{
    public int money=100;
    public void getMoney(){
        System.out.println("金額:" + money);
    }
}

public class Son extends Father{
    public static void main(String[] args) {
        Son son = new Son();
        son.getMoney();
        System.out.println("son 金額=" + son.money);
    }
}

class Animal {
  public void run(int units) {
    System.out.println("動物移動" + units + "步");
  }
}

class Dog extends Animal {
  public void run(int units){
    System.out.println("狗狗跑" + units + "步");
  }
}

import javax.swing.*;

public class Main {
    public static void main(String[] args) {
        JFrame jframe = new JFrame("視窗名稱"); // 產生視窗
        jframe.setSize(視窗寬度, 視窗高度); // 設定視窗大小
        jframe.setVisible(true); // 顯示視窗
    }
}

jframe.setLayout(null);

JLabel label = new JLabel("內容");
JTextField text = new JTextField();
JButton button = new JButton("內容");

import java.net.URL;

ImageIcon image = new ImageIcon(new URL("圖片網址"));
JLabel imageLabel = new JLabel(image);

int imageWight = image.getIconWidth(); // 可得到圖片的寬高
int imageHeight = image.getIconHeight();

import java.net.URL;
import java.awt.*;

ImageIcon icon = new ImageIcon(new URL("icon 網址"));
Image newIcon = icon.getImage().getScaledInstance(寬度, 高度, Image.SCALE_SMOOTH);
icon = new ImageIcon(newIcon);
button.setIcon(icon);

label.setBounds(x, y, width, height);
imageLabel.setBounds(x, y, imageWight, imageHeight);
text.setBounds(x, y, width, height);
button.setBounds(x, y, width, height);

jframe.add(label);
jframe.add(text);
jframe.add(button);

import javax.swing.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

public class Swing {
    private JPanel panel1;
    private JButton button1;

    public Swing() {
        button1.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                JOptionPane.showMessageDialog(panel1, "內容");
            }
        });
    }
}

import javax.swing.*;  
import javax.swing.tree.DefaultMutableTreeNode;  

public class TreeExample {  
    TreeExample() {  
        JFrame frame = new JFrame();   
        
        DefaultMutableTreeNode style = new DefaultMutableTreeNode("Style");  
        DefaultMutableTreeNode color = new DefaultMutableTreeNode("color");  
        DefaultMutableTreeNode font = new DefaultMutableTreeNode("font");  
        
        style.add(color);  // 將 color 加為 style 的子節點
        style.add(font);   // 將 font 加為 style 的子節點
        
        DefaultMutableTreeNode red = new DefaultMutableTreeNode("red");  
        DefaultMutableTreeNode blue = new DefaultMutableTreeNode("blue");  
        DefaultMutableTreeNode black = new DefaultMutableTreeNode("black");  
        DefaultMutableTreeNode green = new DefaultMutableTreeNode("green");  
        
        color.add(red); // 將 red 加為 color 的子節點
        color.add(blue); // 將 blue 加為 color 的子節點
        color.add(black); 
        color.add(green);     
        
        JTree jt = new JTree(style);  // 將 style 作為根節點建構 JTree
        frame.add(jt);  
        frame.setSize(200,200);  
        frame.setVisible(true);  
    }  
    
    public static void main(String[] args) {  
        new TreeExample();  
    }
}

JList list = new JList(new String[]{"a", "b", "c"});

JScrollPane scroll = new JScrollPane(list);

JComboBox combo = new JComboBox();

combo.addItem("內容");

combo.addActionListener(new ActionListener() {
    @Override
    public void actionPerformed(ActionEvent e) {
        // 當選項被選擇時要做的事
    }
});

JTable()
JTable(int numRows, int numColumns)
JTable(Object[][] rowData, Object[] columnNames) //固定資料
JTable(TableModel dm)
JTable(TableModel dm, TableColumnModel cm)
JTable(TableModel dm, TableColumnModel cm, ListSelectionModel sm)
JTable(Vector rowData, Vector columnNames) //可變資料

BorderLayout layout = new BorderLayout();
jframe.setLayout(layout);

jframe.add(元件, "North");

FlowLayout layout = new FlowLayout();
jframe.setLayout(layout);

GridLayout layout = new GridLayout();
jframe.setLayout(layout);

GridLayout layout = new GridLayout(int rows, int cols);
jframe.setLayout(layout);

GridLayout layout = new GridLayout(int rows, int cols, int hgap, int vgap);
jframe.setLayout(layout);

@WebServlet(name = "<servlet_name>", urlPatterns = {"/<網址>"})
public class <servlet_name> extends HttpServlet {
    // do somethings
}

@Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        resp.setContentType("text/html;charset=UTF-8");
        try (PrintWriter out = resp.getWriter()) {
            /* TODO output your page here. You may use following sample code. */
            out.println("<!DOCTYPE html>");
            out.println("<html>");
            out.println("<head>");
            out.println("<title>Servlet HelloServlet</title>");            
            out.println("</head>");
            out.println("<body>");
            out.println("<h1>Servlet WAAAA at " + req.getContextPath() + "</h1>");
            out.println("</body>");
            out.println("</html>");
        }

HttpServletRequest request

getParameter()
getParameterNames()
getParameterValues()

HttpServletResponse response

addHeader()
setContentType()
getWriter()

out.println("<h1> waa" + req.getParameter("name") + "</h1>");

response.setContentType("application/json;charset=utf-8");

Gson gson = new Gson();
out.println(gson.toJson(user));

<% ... %> // 中間編寫 java 語法
<%= ... %> // <% out.println(...); %>
<%@ ... %> // 頁面設定，如 編碼、import...等等