⑴ java编程：如何一行一行读取TXT文档
请看源代码：import java.io.*;
public class Test{
public static void main(String args[])throws Exception{
File file = new File("D:\\Test.java");//Text文件
BufferedReader br = new BufferedReader(new FileReader(file));//构造一个BufferedReader类来读取文件
String s = null;
while((s = br.readLine())!=null){//使用readLine方法回，一次读一行答
System.out.println(s);
}
br.close();;
}
}
⑵ 各位大虾，我想请教一下，java 读取txt 文件时，是一次性读入内存然后一行一行取呢还是一行一行来读的
FileReader ：把文件转换为字符流读入；
BufferedReader会一次性从物理流中读取8k(默认数值,可以设置)字节内容到内存
String line = br.readLine();然后一行一行取
具体看下面网址
⑶ java如何读取一个txt文件的所有内容
import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.io.IOException;
public class ReadFile {
public static void main(String[] args) throws IOException {
String fileContent = readFileContent("");
System.out.println(fileContent);
}
//参数string为你的文件名
private static String readFileContent(String fileName) throws IOException {
File file = new File(fileName);
BufferedReader bf = new BufferedReader(new FileReader(file));
String content = "";
StringBuilder sb = new StringBuilder();
while(content != null){
content = bf.readLine();
if(content == null){
break;
}
sb.append(content.trim());
}
bf.close();
return sb.toString();
}
}
求采纳为满意回答。
⑷ java中如何实现文件的批量读取并提取部分内容写入一个新文件。 单一文件读取写入参照补充
import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
public class Testa
{
public static void main(String[] args)
{
//传入参数为文件目录
test("d:/a.txt");
}
public static void test(String filePath){
BufferedReader br = null;
try {
br = new BufferedReader(new FileReader(filePath));
} catch (FileNotFoundException e) {
e.printStackTrace();
return;
}
String []columnName = {"Id", "Name", "Languages", "Math", "English"}; //列名
int []courseIndexs = {2, 3, 4}; //课程对应的列
int i,j,index;
String line;
List> students = new ArrayList>();
//记录Id和总值,用于排序
List> sortList = new ArrayList>();
try {
br.readLine(); //去掉第一行
while((line = br.readLine()) != null){
index = 0;
String []se = line.split(" ");
Map student = new HashMap();
for(i = 0; i < se.length; i++){
if("".equals(se[i])){
continue;
}
if(index >= columnName.length){
continue;
}
student.put(columnName[index], se[i]);
index++;
}
//计算平均值,总值
double total = 0;
for(j = 0; j < courseIndexs.length; j++){
total += Double.parseDouble((String) student.get(columnName[courseIndexs[j]]));
}
double average = total / courseIndexs.length;
//只取一位小数
average = Math.round(average * 10)/10;
student.put("Total", total);
student.put("Average", average);
Map sort = new HashMap();
sort.put("Id", student.get("Id"));
sort.put("Total", student.get("Total"));
sortList.add(sort);
students.add(student);
}
br.close();
//排序
for(i = 0; i < sortList.size(); i++){
for(j = i + 1; j < sortList.size(); j++){
if((Double)sortList.get(i).get("Total") < (Double)sortList.get(j).get("Total")){
Map temp = sortList.get(i);
sortList.set(i, sortList.get(j));
sortList.set(j, temp);
}
}
}
Map sortedId = new HashMap();
for(i = 0; i < sortList.size(); i++){
sortedId.put(sortList.get(i).get("Id"), i+1);
}
//设定序号
for(j = 0; j < students.size(); j++){
students.get(j).put("Order", sortedId.get(students.get(j).get("Id")));
}
//输出(写到原文件)
//PrintWriter pw = new PrintWriter(new File(filePath));
//输出(写到其他文件)
PrintWriter pw = new PrintWriter(new File("D:/b.txt"));
pw.println("Id\tName\tLan\tMath\tEnglish\tAverage\tTotal\tSort");
int cIndex;
for(i = 0; i < students.size(); i++){
Map st = students.get(i);
cIndex = 0;
pw.println(st.get(columnName[cIndex++]) + "\t" + st.get(columnName[cIndex++])
+ "\t" + st.get(columnName[cIndex++])+ "\t" + st.get(columnName[cIndex++])
+ "\t" + st.get(columnName[cIndex++])
+ "\t" + st.get("Total")
+ "\t" + st.get("Average")
+ "\t" + st.get("Order"));
}
pw.flush();
pw.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
⑸ java 多线程按行读取txt 每个线程读的内容不能重复 求demo
public class Test{
public static void main(String args[])throws Exception{
File file = new File("D:\\Test.java");//Text文件
BufferedReader br = new BufferedReader(new FileReader(file));//构造一个BufferedReader类来读取文件
String s = null;
while((s = br.readLine())!=null){//使用readLine方法版，一次读一行权
System.out.println(s);
}
br.close();;
}
}
⑹ Java编程Scanner读取text文件问题
NoSuchElementException表示元素类型不匹配，你检查下是不是输入的数据不是double类型的或者是在其他地方出现了类型错误