java10.txt

达内IT培训Core Java全部笔记 是学习Java编程的好东西

事件
	所有事件都具有三个要素：
	事件源：一个事件的发起者（按钮）	//落实在类上（组件负责生成事件源，事件源产生时间对象传递给事件监听，监听在对事件源进行处理）
	事件对象：用来描述发生什么事情，是一个描述者，通知JVM发生点击具体事件
	事件监听：一个事件的处理者	//接口（类和接口，接口强制要求他的子类来实现它的方法）监听应该跟事件源打交道

	没有方法的接口：标识接口(EventListener,Cloneable)

	
EventObject:
	ActionEvent（最常用）:点击操作（菜单，按钮），文本框回车，双击List组件
	AdjustmentEvent（基本用不到）
	ComponentEvent（基本用不到）
	ItemEvent:勾选
	TextEvent（用得也不多，因为不适用于swing组件）:文本事件，文本组件中文字的变化
	ContainerEvent:容器事件
	FocusEvent:焦点事件，光标事件
	InputEvent:输入事件（键盘鼠标）
	WindowEvent:窗口事件

所有的监听都是以接口的方式实现的（教程P63）

计数窗口：
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package com.tarena.day10.gui;

import java.awt.FlowLayout;
import java.awt.event.*;

import javax.swing.*;

public class TestCount implements ActionListener{
	private int count = 0;
	JLabel jl = new JLabel("    0次");
	
	public TestCount(){
		JFrame jf = new JFrame("计数器");
		JButton jb1 = new JButton("+");
		JButton jb2 = new JButton("-");
		jb1.addActionListener(this);
		jb2.addActionListener(this);
		
		jf.setLayout(new FlowLayout());
		jf.add(jl);
		jf.add(jb1);
		jf.add(jb2);
		
		jf.pack();
		jf.setVisible(true);
		jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		
	}
	public void actionPerformed(ActionEvent e) {
			String comm = e.getActionCommand();
			if("+".equals(comm)){
				count++;
			}else{
				count--;
			}
			jl.setText(count+"次");		
	}


	public static void main(String[] args) {
			new TestCount();
	}
}
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计算器作业（支持连加/连减/连乘/连除）：
**注意：此程序还有最后一点bug，在连续计算过程中无法更换运算符，否则会计算出错**
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package calculater;

import java.awt.BorderLayout;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.math.BigDecimal;

import javax.swing.*;

public class Calculater implements ActionListener{
	private String[] names = {"Backspace","CE","C","+","7","8","9","-","4","5","6","*","1","2","3","/","0","+/-",".","="};
	private JButton[] jb = new JButton[names.length];
	private boolean append = false;
	private String operator = "+";
	private String s1 = "0";
	private String ss = "0";
	
	JTextField jtf = new JTextField(20);
	
	public Calculater() {}
	public Calculater(String title){
		JFrame jf = new JFrame(title);
		JPanel jp = new JPanel();
		jp.setLayout(new GridLayout(5,4));
		
		for (int i = 0; i < jb.length; i++) {
			jb[i] = new JButton(names[i]);
			jb[i].addActionListener(this);
			jp.add(jb[i]);
		}
		
		jf.add(jtf,BorderLayout.NORTH);
		jf.add(jp);
		jtf.setHorizontalAlignment(JTextField.RIGHT);
		jtf.setText("0");
		jtf.setEditable(false);
		
		jf.pack();
		jf.setVisible(true);
		jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
	}
	
	public void actionPerformed(ActionEvent e) {
		String comm = e.getActionCommand();
		if(comm.matches("\\d")){					//用正则表达式判断输出的是否是0~9			
			if(append){
					String temp = jtf.getText();
					jtf.setText(temp + comm);
			}else{
					jtf.setText(comm);
					append = true;
			}
			
		}else if(comm.equals(".")){
			String temp = jtf.getText();
			if(temp.indexOf(".")== -1 && append){		//当输入的文本中没有小数点
				jtf.setText(temp+comm);
				append = true;										//输入小数点后继续追加
			}else if(!append){			//当字符串开始时候先输入 " . " 则直接输出" 0. "
				jtf.setText("0"+comm);
				append = true;
			}
		}else if("+-*/".indexOf(comm)!= -1){
			operator = comm;
			s1 = jtf.getText();
			double d3 = Double.parseDouble(s1);
			double d4 = Double.parseDouble(ss);
			BigDecimal bd3 = new BigDecimal(d3+"");
			BigDecimal bd4 = new BigDecimal(d4+"");
			if(operator.equals("+")){
				d3 = bd3.add(bd4).doubleValue();
				ss = d3+"";
				jtf.setText(ss);
			}else if(operator.equals("-")){
				if(d4 == 0.0){
					ss = s1;
					jtf.setText(ss);
				}else{
					d3 = bd4.subtract(bd3).doubleValue();
					ss = d3+"";
					jtf.setText(ss);
				}
			}else if(operator.equals("*")){
				if(d4 == 0.0){
					ss = s1;
					jtf.setText(ss);
				}else{
					d3 = bd3.multiply(bd4).doubleValue();
					ss = d3+"";
					jtf.setText(ss);
				}
			}else if(operator.equals("/")){
				if(d4 == 0.0){
					ss = s1;
					jtf.setText(s1);
				}else{
					d3 = bd4.divide(bd3,15,BigDecimal.ROUND_HALF_UP).doubleValue();
				}
				ss = d3+"";
				jtf.setText(ss);				
			}
			append = false;										//不继续追加
		}else if(comm.equals("=")){
			String s2 = jtf.getText();
			double d1 = Double.parseDouble(ss);
			double d2 = Double.parseDouble(s2);
			BigDecimal bd1 = new BigDecimal(d1+"");
			BigDecimal bd2 = new BigDecimal(d2+"");
			if(operator.equals("+")){
				d1 = bd1.add(bd2).doubleValue();
			}else if(operator.equals("-")){
				d1 = bd1.subtract(bd2).doubleValue();
			}else if(operator.equals("*")){
				d1 = bd1.multiply(bd2).doubleValue();
			}else if(operator.equals("/")){		//精确计算浮点除法
				if(d2!=0.0){
					d1 = bd1.divide(bd2,15,BigDecimal.ROUND_HALF_UP).doubleValue();
				}
			}
			ss = "0";
			jtf.setText(d1+"");
			append = false;											//不继续追加
		}else if(comm.equals("CE")||comm.equals("C")){
			jtf.setText("0");
			ss = "0";
			append = false;
		}else if(comm.equals("+/-")){
			String temp = jtf.getText();
			if(!append){
				jtf.setText("-");
				append = true;
			}else if(temp.startsWith("-")){					//如果字符串以负号开头
				jtf.setText(temp.substring(1));
			}else{
				jtf.setText("-" + temp);
			}
		}else if(comm.equals("Backspace")){
			String temp = jtf.getText();
			if(temp.length()>0){
				jtf.setText(temp.substring(0,temp.length()-1));
			}
		}
	}
	
	public static void main(String[] args) {
		new Calculater("Calculater");
	}
}


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int 21亿
long 21亿* 21亿 

用BigDecimal解决浮点运算精度问题，必须用String类型作参数：
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package com.tarena.day10.gui;

import java.math.BigDecimal;

public class TestBigDecimal {

	public static void main(String[] args) {
		double d1 = 1.0;
		double d2 = 0.41;
		System.out.println(d1-d2);
		BigDecimal bd1 = new BigDecimal(d1);
		BigDecimal bd2 = new BigDecimal(d2);
		System.out.println(bd1.subtract(bd2).doubleValue());
		//BigDecimal想要正确解决精度问题就要用String
		BigDecimal bd3 = new BigDecimal(""+d1);
		BigDecimal bd4 = new BigDecimal(""+d2);
		System.out.println(bd3.subtract(bd4).doubleValue());
		BigDecimal bd5 = new BigDecimal("5");
		BigDecimal bd6 = new BigDecimal("3");
		System.out.println(bd5.divide(bd6,5,BigDecimal.ROUND_HALF_UP).doubleValue());
		
		//大数计算
		String a1 = "123456789123456789123456789";
		String a2 = "123456789123456789123456789";
		BigDecimal bd7 = new BigDecimal(a1);
		BigDecimal bd8 = new BigDecimal(a2);
		System.out.println(bd7.add(bd8));

	}
}
输出结果：
0.5900000000000001
0.5900000000000001
0.59
1.66667
246913578246913578246913578
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AWT.Swing中的菜单：
	菜单栏(JMenuBar)，菜单(JMenu)，菜单项(JMenuItem)
-----------------------------------------------------------------------------------------
package com.tarena.day10.gui;

import javax.swing.*;

public class TestMenu {
		public TestMenu(){
			JFrame jf = new JFrame("TestMenu");
			JMenuBar jmb = new JMenuBar();
			String[] jml = {"File","Edit","Help"};
			String[][] jmil = {{"New","Open","Save","Save as","","Exit"},{"ed1","ed2","ed3","","ed4"},{"h1","h2"}};
			JMenu[] jm = new JMenu[jml.length];
			JMenuItem[][] jmi = new JMenuItem[jmil.length][];
			for (int i = 0; i < jml.length; i++) {
				jm[i] = new JMenu(jml[i]);
				jmi[i] = new JMenuItem[jmil[i].length];	//二维数组中会有空指针，要先NEW一次子数组才不会报错
				for (int j = 0; j < jmil[i].length; j++) {
					if(jmil[i][j].equals("")){
						jm[i].addSeparator();			//如果为空增加分割符
					}else{				
						jmi[i][j] = new JMenuItem(jmil[i][j]);
						jm[i].add(jmi[i][j]);
					}
				}
				jmb.add(jm[i]);
			}
			jf.setJMenuBar(jmb);
			jf.setSize(200,100);
			jf.setVisible(true);
			jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		}
	public static void main(String[] args) {
		new TestMenu();
	}
}
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package com.tarena.day10.gui;

import javax.swing.*;
public class GuiUtil {
			public static JMenuBar getMenuBar(	String[] jml,String[][] jmil){
				JMenuBar jmb = new JMenuBar();
				JMenu[] jm = new JMenu[jml.length];
				JMenuItem[][] jmi = new JMenuItem[jmil.length][];
				for (int i = 0; i < jml.length; i++) {
					jm[i] = new JMenu(jml[i]);
					jmi[i] = new JMenuItem[jmil[i].length];
					for (int j = 0; j < jmil[i].length; j++) {
						if(jmil[i][j].equals("")){
							jm[i].addSeparator();
						}else{						
							jmi[i][j] = new JMenuItem(jmil[i][j]);
							jm[i].add(jmi[i][j]);
						}
					}
					jmb.add(jm[i]);
				}
				return jmb;
			}
			public static void main(String[] args){
				JFrame jf = new JFrame("TestMenu");
				String[] jml = {"File","Edit","Help"};
				String[][] jmil = {{"New","Open","Save","Save as","","Exit"},{"ed1","ed2","ed3","","ed4"},{"h1","h2"}};
				JMenuBar jmb = GuiUtil.getMenuBar(jml, jmil);
				jf.setJMenuBar(jmb);
				jf.setSize(200,100);
				jf.setVisible(true);
				jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
			}
}
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适配器类：
	当监听接口方法比较多的时候，就可以写个适配器类作为接口的子类，可以继承这个适配器类并重写其中一个或多个方法，不用强制重写所有方法：
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package com.tarena.day10.gui;

import java.awt.event.WindowEvent;
import java.awt.event.WindowListener;

import javax.swing.JFrame;

public class TestWindowListener1 implements WindowListener{

	public static void main(String[] args){
		JFrame jf = new JFrame();
		jf.setSize(300,100);
		jf.setVisible(true);
		jf.addWindowListener(new TestWindowListener1());
	}

	public void windowActivated(WindowEvent e) {

	}

	public void windowClosed(WindowEvent e) {
	
	}

	public void windowClosing(WindowEvent e) {
		System.out.println("window close");
		System.exit(0);		//非正常退出	
	}

	public void windowDeactivated(WindowEvent e) {
	
	}

	public void windowDeiconified(WindowEvent e) {

	}

	public void windowIconified(WindowEvent e) {

	}

	public void windowOpened(WindowEvent e) {

	}

}
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用适配器类重写其中的一个方法，中间使用匿名内部类：
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package com.tarena.day10.gui;

import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;

import javax.swing.JFrame;

public class TestWindowListener2 {

	public static void main(String[] args) {
		JFrame jf = new JFrame();
		jf.setSize(300,100);
		jf.setVisible(true);
		jf.addWindowListener(new TestWindowListener1());
		jf.addWindowListener(new WindowAdapter(){});		//匿名内部类
	}
	public void windowClosing(WindowEvent e) {
		System.out.println("window close");
		System.exit(0);		//非正常退出	
	}
}
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作业：
写一个菜单栏，要有

文件：
新建/打开/保存/另存/分割线/退出

编辑：
撤销/剪切/复制/粘贴/删除/查找/替换/全选

帮助：
关于记事本

除了打开/保存/另存/新建，其他的都可以做了