文本内容到集合,反之

file的遍历(例题):

package cn.itcast.demo01;

import java.io.File;
/*
* 练习: 给定一个文件夹, 把文件夹里面的所有子文件都打印出来,包含子文件夹里面的文件
* 
* 分析:
* 1. 创建File对象,绑定给定的文件路径
* 2. 调用方法listFiles,获取所有的内容
* 3. 遍历文件数组,判断是文件还是文件夹
* 4. 如果是文件直接打印出来,如果是文件夹继续遍历
*/
public class Demo10FileLoop {

public static void main(String[] args) {
// * 1. 创建File对象,绑定给定的文件路径
File f = new File("C:\Users\sszz\Desktop\aaa");

methodFileLoop(f);
}

public static void methodFileLoop(File f) {
// * 2. 调用方法listFiles,获取所有的内容
File[]listf = f.listFiles();

// * 3. 遍历文件数组,判断是文件还是文件夹
for(File file : listf){
// * 4. 如果是文件直接打印出来,如果是文件夹继续遍历
if(file.isDirectory()){
//调用方法,继续遍历
methodFileLoop(file);
}else{
System.out.println(file);
}
}

}

public static void method2(File f){
File[] listf = f.listFiles();

for (File file : listf) {
if(file.isDirectory()){
// method3(file);
}else{
System.out.println(file);
}
}
}
}

*文本内容存放到集合中,在判断集合中的内容:

package demo01;

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Properties;
import java.util.Set;

public class Test {

public static void main(String[] args) throws IOException {

ArrayList<Book> list =new ArrayList<>();
Properties p = new Properties();
FileReader fis=new FileReader("book.txt");
p.load(fis);

Set<String> set = p.stringPropertyNames();
for (String key : set) {
String[] split = key.split(",");
Book book=new Book(split[0],Double.parseDouble(split[1]),Integer.parseInt(split[2]));
list.add(book);
}
fis.close();

int sumPrice=0;
for (Book book : list) {
System.out.println(book.getName()+","+"共计"+(book.getNums()*book.getPrice())+"元");
sumPrice+=book.getNums()*book.getPrice();
}
System.out.println("		"+"总金额"+sumPrice);
}

}

或者:

package demo04;

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;
import java.util.Properties;
import java.util.Scanner;
import java.util.Set;

public class Test {

public static void main(String[] args) throws IOException {
Properties p= new Properties();
BufferedReader br = new BufferedReader(new FileReader("player.txt"));
p.load(br);
br.close();
Map<String,String> map = new HashMap<>();
Set<String> stringPropertyNames = p.stringPropertyNames();
for (String string : stringPropertyNames) {
String[] s = string.toString().split(",");
map.put(s[0], s[1]);
}
/*Set<Object> keySet = p.keySet();
Map<String,String> map = new HashMap<>();
for(Object o : keySet){
System.out.println(o);
String[] s = o.toString().split(",");
map.put(s[0], s[1]);
}*/
Set<String> keySet2 = map.keySet();
Scanner sc = new Scanner(System.in);
System.out.println("请输入球员名:");
String playerName = sc.nextLine();
if(keySet2.contains(playerName)){
System.out.println(playerName+"所属"+map.get(playerName));
}else{
System.out.println("不存在该球员");
}

}

}

向文本中存放数据

BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream("Student.txt"));
byte[] bufTitle = "姓名	语文成绩	数学成绩	总分".getBytes();    
byte[] buf1 = ("
"+stu1.getName()+"	"+stu1.getChineseScore()+"	"+stu1.getMathScore()).getBytes();
bos.write(bufTitle);
bos.write(buf1);
bos.close();