Java 8 Stream – Read a file line by line
In Java 8, you can use Files.lines to read file as Stream.
c://lines.txt – A simple text file for testing
line1
line2
line3
line4
line5
1. Java 8 Read File + Stream
TestReadFile.java
package com.mkyong.java8;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.stream.Stream;
public class TestReadFile {
public static void main(String args[]) {
String fileName = "c://lines.txt";
//read file into stream, try-with-resources
try (Stream<String> stream = Files.lines(Paths.get(fileName))) {
stream.forEach(System.out::println);
} catch (IOException e) {
e.printStackTrace();
}
}
}
Output
line1
line2
line3
line4
line5
2. Java 8 Read File + Stream + Extra
This example shows you how to use Stream to filter content, convert the entire content to upper case and return it as a List.
TestReadFile2.java
package com.mkyong.java8;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.ArrayList;
import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.Stream;
public class TestReadFile2 {
public static void main(String args[]) {
String fileName = "c://lines.txt";
List<String> list = new ArrayList<>();
try (Stream<String> stream = Files.lines(Paths.get(fileName))) {
//1. filter line 3
//2. convert all content to upper case
//3. convert it into a List
list = stream
.filter(line -> !line.startsWith("line3"))
.map(String::toUpperCase)
.collect(Collectors.toList());
} catch (IOException e) {
e.printStackTrace();
}
list.forEach(System.out::println);
}
}
Output
LINE1
LINE2
LINE4
LINE5
3. BufferedReader + Stream
A new method lines() has been added since 1.8, it lets BufferedReader returns content as Stream.
TestReadFile3.java
package com.mkyong.java8;
import java.io.BufferedReader;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.ArrayList;
import java.util.List;
import java.util.stream.Collectors;
public class TestReadFile3{
public static void main(String args[]) {
String fileName = "c://lines.txt";
List<String> list = new ArrayList<>();
try (BufferedReader br = Files.newBufferedReader(Paths.get(fileName))) {
//br returns as stream and convert it into a List
list = br.lines().collect(Collectors.toList());
} catch (IOException e) {
e.printStackTrace();
}
list.forEach(System.out::println);
}
}
Output
line1
line2
line3
line4
line5
4. Classic BufferedReader And Scanner
Enough of Java 8 and Stream, let revisit the classic BufferedReader (JDK1.1) and Scanner (JDK1.5) examples to read a file line by line, it is working still, just developers are moving toward Stream.
4.1 BufferedReader + try-with-resources example.
TestReadFile4.java
package com.mkyong.core;
import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
public class TestReadFile4{
public static void main(String args[]) {
String fileName = "c://lines.txt";
try (BufferedReader br = new BufferedReader(new FileReader(fileName))) {
String line;
while ((line = br.readLine()) != null) {
System.out.println(line);
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
4.2 Scanner + try-with-resources example.
TestReadFile5.java
package com.mkyong.core;
import java.io.File;
import java.io.IOException;
import java.util.Scanner;
public class TestReadFile5 {
public static void main(String args[]) {
String fileName = "c://lines.txt";
try (Scanner scanner = new Scanner(new File(fileName))) {
while (scanner.hasNext()){
System.out.println(scanner.nextLine());
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
from:http://www.mkyong.com/java8/java-8-stream-read-a-file-line-by-line/
In Java 8, you can use Files.lines
to read file as Stream
.
line1
line2
line3
line4
line5
1. Java 8 Read File + Stream
package com.mkyong.java8;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.stream.Stream;
public class TestReadFile {
public static void main(String args[]) {
String fileName = "c://lines.txt";
//read file into stream, try-with-resources
try (Stream<String> stream = Files.lines(Paths.get(fileName))) {
stream.forEach(System.out::println);
} catch (IOException e) {
e.printStackTrace();
}
}
}
Output
line1
line2
line3
line4
line5
Java 8 Stream – Read a file line by line的更多相关文章
- Java - 17 Java 流(Stream)、文件(File)和IO
Java 流(Stream).文件(File)和IO Java.io包几乎包含了所有操作输入.输出需要的类.所有这些流类代表了输入源和输出目标. Java.io包中的流支持很多种格式,比如:基本类型. ...
- Java笔记:Java 流(Stream)、文件(File)和IO
更新时间:2018-1-7 12:27:21 更多请查看在线文集:http://android.52fhy.com/java/index.html java.io 包几乎包含了所有操作输入.输出需要的 ...
- Java总结:Java 流(Stream)、文件(File)和IO
更新时间:2018-1-7 12:27:21 更多请查看在线文集:http://android.52fhy.com/java/index.html java.io 包几乎包含了所有操作输入.输出需要的 ...
- Java 流(Stream)、文件(File)和IO
Java.io包几乎包含了所有操作输入.输出需要的类.所有这些流类代表了输入源和输出目标. Java.io包中的流支持很多种格式,比如:基本类型.对象.本地化字符集等等. 一个流可以理解为一个数据的序 ...
- java学习笔记(九):Java 流(Stream)、文件(File)和IO
Java 的控制台输入由 System.in 完成. 为了获得一个绑定到控制台的字符流,你可以把 System.in 包装在一个 BufferedReader 对象中来创建一个字符流.需要import ...
- Java流(Stream)、文件(File)和IO
Java.io包几乎包含了所有操作输入.输出需要的类.所有这些流类代表了输入源和输出目标. Java.io包中的流支持很多格式,比如:基本类型.对象.本地化字符集等等. 一个流可以理解为一个数据的序列 ...
- Java 流(Stream)、文件(File)和IO -- Java ByteArrayOutputStream类
Java ByteArrayOutputStream类 字节数组输出流在内存中创建一个字节数组缓冲区,所有发送到输出流的数据保存在该字节数组缓冲区中.创建字节数组输出流对象有以下几种方式. 下面的构造 ...
- Java ——流(Stream)、文件(File)和IO
本节重点思维导图 示例:将指定的字符写到文件中 public static void main(String[] args) { try { //1.创建一个空的文件 File file = new ...
- Java 流(Stream)、文件(File)和IO -- Java ByteArrayInputStream类
字节数组输入流在内存中创建一个字节数组缓冲区,从输入流读取的数据保存在该字节数组缓冲区中.创建字节数组输入流对象有以下几种方式. 接收字节数组作为参数创建: ByteArrayInputStream ...
随机推荐
- Initialization failed for Block pool <registering> (Datanode Uuid unassigned) service to IP1:8020 Invalid volume failure config value: 1
2017-02-27 16:19:44,739 ERROR datanode.DataNode: Initialization failed for Block pool <registerin ...
- 微信小程序 - (下拉)加载更多数据
注意和后端配合就行了,前端也只能把数据拼接起来! 无论是下拉加载还是加载更多,一样的道理! 注意首次加载传递参数 注意每次加载数据数 wxml <view class='table-rank'& ...
- SpringBoot启动器详解pom.xml
Spring Boot应用启动器基本的一共有44种,具体如下: 1)spring-boot-starter 这是Spring Boot的核心启动器,包含了自动配置.日志和YAML. 2)spring- ...
- 【Zookeeper】源码分析之请求处理链(三)之SyncRequestProcessor
一.前言 在分析了PrepRequestProcessor处理器后,接着来分析SyncRequestProcessor,该处理器将请求存入磁盘,其将请求批量的存入磁盘以提高效率,请求在写入磁盘之前是不 ...
- 解决 nfs挂载错误wrong fs type, bad option, bad superblock
yum install nfs-utils mount -t nfs 192.168.1.153:/taimei /taimei
- vim note write
Try: :vert sb N which will open a left vertical split (by default, unless you have modified some opt ...
- stardict dict url
http ://download.huzheng.org/zh_CN/ tar -xjvf a.tar.bz2 -C /usr/share/stardict/dic
- Linux中wget用法
Wget简介:Linux系统中wget是一个下载文件的工具,它用在命令行下.对于Linux用户是必不可少的工具,我们经常要下载一些软件或从远程服务器恢复备份到本地服务器.wget支持HTTP,HTTP ...
- django之创建第7-1个项目-url配置高级
修改urls.PY文件 # -*- coding: UTF-8 -*- from django.conf.urls import patterns, include, url # Uncomment ...
- C++基础学习教程(六)----类编写的前情回想以及项目实战(1)
在開始类的编写之前我们依旧须要回想整理一下前面所说的内容,(前面尽管是一个自己定义数据类型的实现过程,可是内容有点繁杂). 先看一段代码: /** @file calssStruct.cpp */ / ...