随机访问文件
RandomAccessFile: 可在文件任何位置读写文件，通过设置读写参数"rw"，判断可进行的操作。
作者提供的示例(close关闭部分有修改)：
RandomFileTest.java
❤🧡💛💚💙💜🤎🖤❤🧡💛💚💙💜🤎🖤❤🧡💛💚💙💜🤎🖤
import java.io.*;
public class RandomFileTest {
public static void main(String[] args) {
Employee[] staff = new Employee[3];
staff[0] = new Employee("Carl Cracker", 75000,1987, 12, 15);
staff[1] = new Employee("Harry Hacker", 50000, 1989, 10, 1);
staff[2] = new Employee("Tony Tester", 40000, 1990, 3, 15);
DataOutputStream out = null;
RandomAccessFile in = null;
try{
out = new DataOutputStream(new FileOutputStream("employee.dat"));
for(Employee e:staff)
e.writeData(out);
in = new RandomAccessFile("employee.dat", "r");
int n = (int)(in.length()/Employee.RECORD_SIZE);
Employee[] newStaff = new Employee[n];
for(int i = n-1; i >= 0; i--){
newStaff[i] = new Employee();
in.seek(i*Employee.RECORD_SIZE);
newStaff[i].readData(in);
}
for(Employee e:newStaff)
System.out.println(e);
}catch (IOException e){
e.printStackTrace();
}finally {
close(out);
close(in);
}
}
private static void close(Closeable c){
if(c == null) return;
try {
c.close();
} catch (IOException ex) {
ex.printStackTrace();
}
}
}
❤🧡💛💚💙💜🤎🖤❤🧡💛💚💙💜🤎🖤❤🧡💛💚💙💜🤎🖤
Employee.java
❤🧡💛💚💙💜🤎🖤❤🧡💛💚💙💜🤎🖤❤🧡💛💚💙💜🤎🖤
import java.io.*;
public class RandomFileTest {
public static void main(String[] args) {
Employee[] staff = new Employee[3];
staff[0] = new Employee("Carl Cracker", 75000,1987, 12, 15);
staff[1] = new Employee("Harry Hacker", 50000, 1989, 10, 1);
staff[2] = new Employee("Tony Tester", 40000, 1990, 3, 15);
DataOutputStream out = null;
RandomAccessFile in = null;
try{
out = new DataOutputStream(new FileOutputStream("employee.dat"));
for(Employee e:staff)
e.writeData(out);
in = new RandomAccessFile("employee.dat", "r");
int n = (int)(in.length()/Employee.RECORD_SIZE);
Employee[] newStaff = new Employee[n];
for(int i = n-1; i >= 0; i--){
newStaff[i] = new Employee();
in.seek(i*Employee.RECORD_SIZE);
newStaff[i].readData(in);
}
for(Employee e:newStaff)
System.out.println(e);
}catch (IOException e){
e.printStackTrace();
}finally {
close(out);
close(in);
}
}
private static void close(Closeable c){
if(c == null) return;
try {
c.close();
} catch (IOException ex) {
ex.printStackTrace();
}
}
}
❤🧡💛💚💙💜🤎🖤❤🧡💛💚💙💜🤎🖤❤🧡💛💚💙💜🤎🖤
运行结果：
🚗🚓🚕🛺🚙🚌🚐🚎🚑🚒🚚🚛🚜🚘🚔🚖🚍🦽🦼🛹🚲🛴🛵🏍
🚗🚓🚕🛺🚙🚌🚐🚎🚑🚒🚚🚛🚜🚘🚔🚖🚍🦽🦼🛹🚲🛴🛵🏍
1.4 ZIP文档
ZipInputStream/ZipOutputStream 可以处理 Zip 文档的压缩
特别注意对于单条信息的关闭方法：zin.closeEntry()
❤🧡💛💚💙💜🤎🖤❤🧡💛💚💙💜🤎🖤❤🧡💛💚💙💜🤎🖤
import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.util.List;
import java.util.Scanner;
import java.util.zip.ZipEntry;
import java.util.zip.ZipInputStream;
public class ZipTest {
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
ZipTestFrame frame = new ZipTestFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}
});
}
}
class ZipTestFrame extends JFrame {
private int WIDTH = 400;
private int HEIGHT = 300;
private JComboBox fileCombo;
private JTextArea fileText;
private String zipname;
public ZipTestFrame(){
setTitle("ZipTest");
setSize(WIDTH,HEIGHT);
JMenuBar menuBar = new JMenuBar();
JMenu menu = new JMenu("File");
JMenuItem openItem = new JMenuItem("Open");
menu.add(openItem);
openItem.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
JFileChooser chooser = new JFileChooser();
chooser.setCurrentDirectory(new File("."));
int r = chooser.showOpenDialog(ZipTestFrame.this);
if(r == JFileChooser.APPROVE_OPTION){
zipname = chooser.getSelectedFile().getPath();
fileCombo.removeAllItems();
scanZipFile();
}
}
});
JMenuItem exitItem = new JMenuItem("Exit");
menu.add(exitItem);
exitItem.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
System.exit(0);
}
});
menuBar.add(menu);
setJMenuBar(menuBar);
fileText = new JTextArea();
fileCombo = new JComboBox();
fileCombo.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
loadZipFile((String)fileCombo.getSelectedItem());
}
});
add(fileCombo,BorderLayout.SOUTH);
add(new JScrollPane(fileText),BorderLayout.CENTER);
}
public void scanZipFile(){
new SwingWorker<Void, String>(){
@Override
protected Void doInBackground() throws Exception {
ZipInputStream zin = new ZipInputStream(new FileInputStream(zipname));
ZipEntry entry;
while((entry = zin.getNextEntry())!=null){
publish(entry.getName());
zin.closeEntry();
}
zin.close();
return null;
}
@Override
protected void process(List<String> names) {
for(String name:names){
fileCombo.addItem(name);
}
}
}.execute();
}
public void loadZipFile(final String name){
fileCombo.setEnabled(false);
fileText.setText("");
new SwingWorker<Void,Void>(){
@Override
protected Void doInBackground() throws Exception {
try{
ZipInputStream zin = new ZipInputStream(new FileInputStream(zipname));
ZipEntry entry;
while((entry = zin.getNextEntry())!=null){
if(entry.getName().equals(name)){
Scanner in = new Scanner(zin);
while(in.hasNextLine()){
fileText.append(in.nextLine());
fileText.append("\n");
}
}
zin.closeEntry();
}
}catch (IOException e){
e.printStackTrace();
}
return null;
}
@Override
protected void done() {
fileCombo.setEnabled(true);
}
}.execute();
}
}
❤🧡💛💚💙💜🤎🖤❤🧡💛💚💙💜🤎🖤❤🧡💛💚💙💜🤎🖤
运行结果：
读取zip文件内部的文件（一层）
通过下拉框可选择文件名，上方显示文件内容
🚗🚓🚕🛺🚙🚌🚐🚎🚑🚒🚚🚛🚜🚘🚔🚖🚍🦽🦼🛹🚲🛴🛵🏍
实际结构：
🚗🚓🚕🛺🚙🚌🚐🚎🚑🚒🚚🚛🚜🚘🚔🚖🚍🦽🦼🛹🚲🛴🛵🏍
注意，因为新建文件夹不是文件，所以读不出来可考虑使用递归结构继续读取子文件
相关内容：选择 《Java核心技术 卷1》查找相关笔记
评论🌹点赞👍收藏✨关注👀，是送给作者最好的礼物，愿我们共同学习，一起进步
公众号 钰娘娘知识汇总
