java对txt文件增删改查

Ⅰ java 如何对读入的txt文件进行修改啊。。。

这个是一行行读的吧，读到第一行的时候按位置修改分数，然后再输出一个txt覆盖掉原来的

Ⅱ 用JAVA实现对txt文件文本增删改查

正好今天写了个~原来是两个类，好吧，加一个...= =~囧
以文件的形式存储的

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import java.util.Arrays;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Scanner;
import java.util.Set;

public class StudentManager {
private static File DB = new File("students.db");
private static Set<Student> studentList = null;

@SuppressWarnings("unchecked")
private static void initStudentList() {
if (DB.exists()) {
FileInputStream fi = null;
ObjectInputStream oi = null;
try {
fi = new FileInputStream(DB);
oi = new ObjectInputStream(fi);
Object obj = oi.readObject();
fi.close();
oi.close();
if (obj instanceof Set)
studentList = (Set<Student>) obj;
} catch (Exception e) {
e.printStackTrace();
}
}
if (studentList == null)
studentList = new HashSet<Student>();
}

private static void save() {
if (studentList == null)
return;
if (!DB.exists())
try {
DB.createNewFile();
} catch (Exception e) {
e.printStackTrace();
}
FileOutputStream fo;
try {
fo = new FileOutputStream(DB);
ObjectOutputStream oo = new ObjectOutputStream(fo);
oo.writeObject(studentList);
fo.close();
oo.close();
} catch (Exception e) {
e.printStackTrace();
}
}

private static Student[] getStudents(int id, String name) {
HashSet<Student> rlt = new HashSet<Student>();
if (id != 0) {
for (Student s : studentList) {
if (s.id == id)
rlt.add(s);
}
} else if (name != null && !name.isEmpty()) {
for (Student s : studentList) {
if (s._name.equalsIgnoreCase(name))
rlt.add(s);
}
}
return rlt.toArray(new Student[0]);
}

static {
initStudentList();
}
static void out(Object obj){
System.out.println(obj);
}

public static void menu() {
out("Welcome to use Student Manager!\n1-search student;\t2-add student;\t3-list all students;\nothers-exit");
Scanner in = new Scanner(System.in);
Student student = null;
String input = in.nextLine();
if (input.equals("1")) {
Student[] students = new Student[0];
out("please input name/id");
String ins = in.nextLine();
if (ins.matches("\\d+"))
students = getStudents(Integer.parseInt(ins), null);
else
students = getStudents(0, ins);
if (students.length != 0) {
out(Arrays.toString(students).replaceAll(
"\\[|\\]|, ", "\n"));
if (students.length == 1)
student = students[0];
else {
out("please choose a student by id:\n");
int i = in.nextInt();
for (Student s : students) {
if (s.id == i) {
student = s;
break;
} else {
out("error");
menu();
}
}
}
out("1-set score;\t2-delete score;\t3-delete student;\tother-exit");
int input1=in.nextInt();
in.nextLine();
String course=null;
float score=0;
switch(input1){
case 1:
out("please input course");
course=in.nextLine();
out("please input score");
score = in.nextFloat();
in.nextLine();
student.setScore(course, score);
break;
case 2:
out("please input course");
course=in.nextLine();
student.removeScore(course);
break;
case 3:
student.removeFrom(studentList);
break;
}
}
else {
out("NO current record!");
}
}
if (input.equals("2")) {
out("please input id");
int id=in.nextInt();
in.nextLine();
out("please input name");
String name = in.nextLine();
out("please input class");
String cname=in.nextLine();
student=new Student(id, name, cname);
if(studentList.add(student)){
out("create success!\n");
String input2="-";
while(!input2.isEmpty()){
out("set score? \n1-yes;\t2-no");
input2=in.nextLine();
if(input2.equals("1")){
out("please input course");
String course=in.nextLine();
out("please input score");
float score = in.nextFloat();
student.setScore(course, score);
in.nextLine();
}
else break;
}
}else out("Error: id or student exists");
}
if (input.equals("3")) {
out(studentList.toString().replaceAll("\\[|\\]|, ", "\n"));
}
if(input.isEmpty())return;
save();
menu();
}

public static void main(String[] args){
menu();
}
}

class Student implements Serializable {
public String toString() {
return "id: " + id + "\tclass: " + _class + "\tname: " + _name
+ courses.toString().replaceAll("\\{|\\}|, ", "\n").replaceAll("=", ": ");
}

Student(int id, String _name, String _class) {
this.id = id;
this._class = _class;
this._name = _name;
}

private static final long serialVersionUID = 1L;
public int id = 0;

public String _name = "";
public String _class = "";
HashMap<String, Float> courses = new HashMap<String, Float>();

void setScore(String course, float score) {
courses.put(course, score);
System.out.println("set success!\n\n"+this);
}

void removeScore(String course) {
courses.remove(course);
System.out.println("delete success!\n\n"+this);
};

void removeFrom(Set<?> list) {
list.remove(this);
System.out.println("delete success!");
}

public int hashCode() {
return 31;
}

public boolean equals(Object obj) {
Student s = null;
if(obj instanceof Student){
System.out.println(1);
s=(Student)obj;
return s.id==id||(s._class.equals(_class)&&s._name.equals(_name));
}
return false;
}
}
class DaJiangYou{
DaJiangYou(){
System.out.println("I am da jiang you");
}
}

Ⅲ java文件流txt文档内容增删改

import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.List;

public class UpdateTxt {

static List<String> txt = new ArrayList<String>();
public static void main(String[] args) {
read("D:/lj/12.txt");
// add(2,"asd");
delete(2);
// addToFinal("asd");
write("D:/lj/12.txt");
}
//读取
public static void read(String path){
String temp = null;
int i = 0;
try {
BufferedReader br = new BufferedReader(new InputStreamReader(new FileInputStream(path)));
while((temp = br.readLine()) != null){
txt.add(temp);
}
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
//写回
public static void write(String path){
try {
PrintWriter pw = new PrintWriter(new OutputStreamWriter(new FileOutputStream(path)));
for(int i = 0; i<txt.size() ; i++){
pw.println(txt.get(i));
pw.flush();
}
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
//添加到第几行
public static void add(int line , String s){
txt.add(line-1, s);
}
//删除某行
public static void delete(int line){
txt.remove(line - 1);
}

//添加到最后
public static void addToFinal(String s){
txt.add(s);
}

}

Ⅳ java io流对文件的增删改查

可以通过BufferedReader 流的形式进行流读取，之后通过readLine方法获取到的内容,之后通过if判断来实现在某些特定位置的查找、增加、删除、修改操作。
举例：
BufferedReader bre = null;
OutputStreamWriter pw = null;//定义一个流
try {
String file = "D:/test/test.txt";
bre = new BufferedReader(new FileReader(file));//此时获取到的bre就是整个文件的缓存流
pw = new OutputStreamWriter(new FileOutputStream(“D:/test.txt”),"GBK");//确认流的输出文件和编码格式，此过程创建了“test.txt”实例
while ((str = bre.readLine())!= null) // 判断最后一行不存在，为空结束循环
{
if(str.indexOf("排除")<0){//判断是否需要舍弃
pw.write(str);//将要写入文件的内容，可以多次write
}
}
bre.close();//关闭流
pw.close();//关闭流
解释：以上方法是实现的删除，if中的条件改变下，即可实现其余的功能。
备注：文件流用完之后必须及时通过close方法关闭，否则会一直处于打开状态，直至程序停止，增加系统负担。

Ⅳ 如何通过java实现对指定目录下的txt文件进行增删改查

代码如下：

importjava.io.BufferedReader;
importjava.io.BufferedWriter;
importjava.io.FileInputStream;
importjava.io.FileOutputStream;
importjava.io.IOException;
importjava.io.InputStreamReader;
importjava.io.OutputStreamWriter;
importjava.util.ArrayList;
importjava.util.List;

publicclassApp61{

	publicstaticvoidmain(String[]args)throwsIOException{
		
		//查找行输出
		Stringline=findFileLine("mylist.txt","abc");
		System.out.println(line);
		
		//删除指定行
		removeFileLine("mylist.txt",2);
	}
	
	staticvoidremoveFileLine(Stringfile,intline)throwsIOException{
		
		List<String>lines=readFileLines(file);
		
		lines.remove(line-1);
		
		FileOutputStreamoutputStream=null;
		
		=null;
		
		BufferedWriterwriter=null;
		
		try{
			
			outputStream=newFileOutputStream(file);
			
			streamWriter=newOutputStreamWriter(outputStream);
			
			writer=newBufferedWriter(streamWriter);
			
			for(Stringstr:lines){
				writer.write(str+System.lineSeparator());
			}
			
		}finally{
			if(writer!=null){
				writer.close();
			}
			if(streamWriter!=null){
				streamWriter.close();
			}
			if(outputStream!=null){
				outputStream.close();
			}
		}
	}
	
	
	//查找行
	staticStringfindFileLine(Stringfile,Stringkeywork)throwsIOException{
		
		List<String>lines=readFileLines(file);
		
		for(Stringline:lines){
			if(line.contains(keywork)){
				returnline;
			}
		}
		
		return"";
	}
	
	//返回文件所有行
	staticList<String>readFileLines(Stringfile)throwsIOException{
		
		List<String>lines=newArrayList<>();
		
		FileInputStreaminputStream=null;
		
		InputStreamReaderstreamReader=null;
		
		BufferedReaderreader=null;
		
		try{
			
			inputStream=newFileInputStream(file);
			
			streamReader=newInputStreamReader(inputStream);
			
			reader=newBufferedReader(streamReader);
			
			Stringline="";
			
			while((line=reader.readLine())!=null){
				lines.add(line);
			}
		}finally{
			if(reader!=null){
				reader.close();
			}
			if(streamReader!=null){
				streamReader.close();
			}
			if(inputStream!=null){
				inputStream.close();
			}
		}
		
		returnlines;
	}
}

Ⅵ Java实现对txt的增删改查中，怎么把txt中重名的几条信息都删了。比如txt中有好多人的信息，

1. 使用java读取txt文件,使用List集合

2. 判断List集合中重复信息,如果重复,删除

3. 请采纳 谢谢

   publicstaticvoidmain(String[]args){
   List<String>values=newArrayList<String>();
   
   Map<String,Boolean>map=newHashMap<String,Boolean>();
   
   try{
   BufferedReaderbf=newBufferedReader(newInputStreamReader(newFileInputStream("d:/d.txt")));
   Stringvalue="";
   while((value=bf.readLine())!=null){
   value=value.trim();
   if(!value.equals("")){
   if(map.get(value)==null){
   values.add(value);
   map.put(value,true);
   }
   }
   }
   for(Stringstring:values){
   System.out.println(string);
   }
   }catch(FileNotFoundExceptione){
   //TODOAuto-generatedcatchblock
   e.printStackTrace();
   }catch(IOExceptione){
   //TODOAuto-generatedcatchblock
   e.printStackTrace();
   }
   
   }
   

Ⅶ 用java在txt文件下对文件进行增删改查，是否需要用流先给txt文件读入

一般来说，只要不是对文件进行读写，是不需要流的。但涉及到文件内容的读和写，肯定需要流

Ⅷ 用java读写txt格式文件里的数据，并实现对数据的增删改查，求大神知道一二，小弟刚涉足，不是太懂。，

实体类：
AAA属性 id,testDate,road,num1,type1,num2,type2 记得添加get，set方法.
每读取一行时值添加到AAA实体类对应属性中，然后add至List。

楼主用好StringTokenizer 不建议用了，用string.split()方法吧 。
循环：
AAA bean = null;
List<AAA> list = new ArrayList<AAA>();
while (...)
{
bean = new AAA();
String[] arr = s.split("空格数自定");
String id = arr[0].trim();
String testDate= arr[1].trim();//考虑是否转为时间格式
//依次读取

//将读取的值录入到bean中
bean.setId(id);
bean.setTestDate(testDate);
//...依次录入

list.add(bean);//将值添加到集合中
}
//OK ，真累！

Ⅸ 用java在图形用户界面下的txt文件下对文件进行增删改查

就写个新增的吧。其他你照着写。

package com.zz.jfram;

import java.awt.BorderLayout;
import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.File;
import java.io.IOException;

import javax.swing.JButton;
import javax.swing.JFileChooser;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextArea;
import javax.swing.JTextField;

public class TxtManage extends JFrame {

private static final long serialVersionUID = 1L;

public TxtManage() {
final JFrame jFrame = new JFrame();
JButton jButton = new JButton("新增");
JPanel jPanel = new JPanel();
final JTextField jTextField = new JTextField(30);
final JLabel jLabel = new JLabel("请输入新增文件的名字:");
jPanel.add(jLabel, FlowLayout.LEFT);
jPanel.add(jTextField, FlowLayout.CENTER);
jPanel.add(jButton, FlowLayout.RIGHT);
jFrame.add(jPanel, BorderLayout.NORTH);
// 设置窗体属性
jFrame.setBounds(500, 50, 600, 400);
final JTextArea jTextArea = new JTextArea(50, 50);

// 新增按钮点击事件
jButton.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
JFileChooser jfc = new JFileChooser();
jfc.setDialogTitle("选择路径");
jfc.setFileSelectionMode(JFileChooser.DIRECTORIES_ONLY);// 只能选择目录
if (jfc.showOpenDialog(jFrame) == JFileChooser.APPROVE_OPTION) {
// 选中目录的绝对路径
String path = jfc.getSelectedFile().getAbsolutePath();
// 在当前目录新增一个文件
File file = new File(path+"\\"+jTextField.getText()+".txt");
if (!file.exists()) {
try {
file.createNewFile();
jTextArea.setText("文件新增成功！");
} catch (IOException e1) {
e1.printStackTrace();
}
}else{
try {
throw new Exception("文件已存在!");
} catch (Exception e1) {
e1.printStackTrace();
}
}

}
}
});
jFrame.add(jTextArea, BorderLayout.CENTER);
jFrame.setVisible(true);
// 关闭处理动作
jFrame.setDefaultCloseOperation(EXIT_ON_CLOSE);
}

public static void main(String[] args) {
new TxtManage();
}

}

Ⅹ 用Java写一个基于txt文本的控制台输入的增删查改

packagecom.list;
/*
*Author:qcq
*Date:2015/7/20
*E-mail:[email protected]
**/
importjava.io.BufferedReader;
importjava.io.File;
importjava.io.FileReader;
importjava.io.FileWriter;
importjava.io.IOException;
importjava.util.HashMap;
importjava.util.Map;
importjava.util.Scanner;
importjava.util.Set;

publicclassQuery{
	classPerson{
		publicStringId;/*shouldbesurethisisunique*/
		publicStringname;
		publicintage;
		publicbooleansex;/*trueforman,falseforgirl*/
		@Override
		publicStringtoString(){
			returnId+""+name+""+age+""+(sex?"M":"F");
		}
		
	}
	privateMap<String,Person>people;
	privateStringfileName;
	publicQuery(StringfileName){
		people=newHashMap<String,Person>();
		this.fileName=fileName;
		if(!initial()){
			System.out.println(""
					+"storefilepath,pleasecheckit,andrerunthisprogram.");
		}
	}
	privatebooleaninitial(){
		booleanflag=false;
		try{
			Filefile=newFile(fileName);
			if(!file.exists()){
				System.out.println("Thefilenotexist,wewillcreateitforyou");
				file.createNewFile();
			}
			BufferedReaderreader=newBufferedReader(newFileReader(fileName));
			Stringline=reader.readLine();	
			while(null!=line&&!line.equals("")){
				String[]splitLine=line.split("+");
				if(splitLine.length<4){
					System.out.println("Theinformationnotenough");
					returnflag;
				}
				Persontemp=newPerson();
				temp.Id=splitLine[0];
				temp.name=splitLine[1];
				temp.age=Integer.valueOf(splitLine[2]);
				temp.sex=splitLine[3].equals("M")?true:false;
				people.put(temp.Id,temp);
				line=reader.readLine();
			}
			flag=true;
		}catch(IOExceptione){
			e.printStackTrace();
		}
		returnflag;
	}
	publicbooleanwriteInFile(){
		booleanflag=false;
		try{
			FileWriterwriter=newFileWriter(fileName);
			Set<String>key=people.keySet();
			for(StringkeyIndex:key){
				writer.write(people.get(keyIndex).toString()+"
");
			}
		}catch(IOExceptione){
			e.printStackTrace();
		}
		
		returnflag;
	}
	/**/
	publicbooleanadd(){
		returnfalse;
	}
	publicbooleandelete(){
		returnfalse;
	}
	publicbooleanquery(){
		returnfalse;
	}
	publicbooleanupdate(){
		returnfalse;
	}
	publicstaticvoidmain(String[]args){
		Querydata=newQuery("temp.txt");/*hereshoulddefinethefilename*/
		Scannerin=newScanner(System.in);
		System.out.println("Hereyoucanchoicewhichoption:
"
				+"quit:forquit"
				+"a:foradd"
				+"d:fordelete"
				+"u:forupdate"
				+"q:forquery");
		Stringoption=in.next();
		label:
		while(null!=option&&!option.equals("")){
			switch(option){
				case"quit":breaklabel;
				case"a":
					/*hereaddthefunction*/
					data.add();
					break;
				case"d":
					/*hereaddthefunction*/
					data.delete();
					break;
				case"u":
					/*hereaddthefunction*/
					data.update();
					break;
				case"q":
					/*hereaddthefunction*/
					data.query();
					break;
				default:
					breaklabel;	
			}
		}
		if(null!=in){
			in.close();
		}
	}
}