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feat: - [Java 读取文件](https://www.wdbyte.com/java/io/file-read/)
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‎README.md‎

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## Java I/O 教程
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- [Java 创建和写入文件](https://www.wdbyte.com/java/io/file-create-write/)
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- [Java 读取文件](https://www.wdbyte.com/java/io/file-read/)
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## Java 进阶
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- [ProcessBuilder API 使用教程](https://www.wdbyte.com/java/os/processbuilder/)

‎core-java-modules/core-java-io/README.md‎

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当前模块包含 IO 相关代码
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### 相关文章
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- [Java 读取文件](https://www.wdbyte.com/java/io/file-read/)
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- [Java 创建和写入文件](https://www.wdbyte.com/java/io/file-create-write/)
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- [字符图案，我用字符画个冰墩墩](https://www.wdbyte.com/java/char-image.html)

‎core-java-modules/core-java-io/src/main/java/com/wdbyte/io/file/FileReadDemo.java‎

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package com.wdbyte.io.file;
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import java.io.BufferedInputStream;
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import java.io.BufferedReader;
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import java.io.File;
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import java.io.FileInputStream;
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import java.io.FileNotFoundException;
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import java.io.FileReader;
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import java.io.IOException;
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import java.nio.charset.StandardCharsets;
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import java.nio.file.Files;
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import java.nio.file.Path;
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import java.nio.file.Paths;
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import java.util.List;
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import java.util.Scanner;
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import java.util.stream.Stream;
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import org.junit.jupiter.api.Test;
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/**
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* @author niulang
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* @date 2023/11/08
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*/
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public class FileReadDemo {
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public static void main(String[] args) {
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Path path = Paths.get("/Users/darcy/wdbyte");
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System.out.println(Files.isDirectory(path));
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System.out.println(path.toFile().isFile());
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System.out.println(path.toFile().isDirectory());
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}
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/**
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* java 8
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*
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* @throws IOException
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*/
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@Test
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public void test1() throws IOException {
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Path path = Paths.get("/Users/darcy/wdbyte/log.txt");
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List<String> lines = Files.readAllLines(path, StandardCharsets.UTF_8);
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for (String line : lines) {
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System.out.println(line);
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}
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}
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/**
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* java 8
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*
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* @throws IOException
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*/
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@Test
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public void test2() throws IOException {
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Path path = Paths.get("/Users/darcy/wdbyte/log.txt");
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byte[] bytes = Files.readAllBytes(path);
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String content = new String(bytes, StandardCharsets.UTF_8);
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System.out.println(content);
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}
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/**
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* java 8
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*
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* @throws IOException
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*/
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@Test
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public void test3() throws IOException, InterruptedException {
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Path path = Paths.get("/Users/darcy/wdbyte/log.txt");
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try (Stream<String> stream = Files.lines(path);) {
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stream.forEach(System.out::println);
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}
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try (Stream<String> stream = Files.lines(path);) {
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stream.parallel().forEachOrdered(System.out::println);
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}
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}
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/**
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* java 11
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* 要求：文件小于2G
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*
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* @throws IOException
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*/
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@Test
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public void test4() throws IOException {
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Path path = Paths.get("/Users/darcy/wdbyte/log.txt");
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String content = Files.readString(path, StandardCharsets.UTF_8);
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System.out.println(content);
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}
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@Test
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public void test5() {
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File file = new File("/Users/darcy/wdbyte/log.txt");
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String line;
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// 默认读取缓冲区大小 8K
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try (BufferedReader br = new BufferedReader(new FileReader(file))) {
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while ((line = br.readLine()) != null) {
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System.out.println(line);
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}
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} catch (FileNotFoundException e) {
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throw new RuntimeException(e);
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} catch (IOException e) {
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throw new RuntimeException(e);
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}
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// 定义缓冲区大小为 128 K
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int buffer = 128 * 1024;
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try (BufferedReader br = new BufferedReader(new FileReader(file), buffer)) {
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while ((line = br.readLine()) != null) {
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System.out.println(line);
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}
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} catch (FileNotFoundException e) {
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throw new RuntimeException(e);
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} catch (IOException e) {
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throw new RuntimeException(e);
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}
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}
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/**
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* java 8
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*
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* @throws IOException
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*/
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@Test
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public void test6() throws IOException {
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Path path = Paths.get("/Users/darcy/wdbyte/log.txt");
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String line;
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try (BufferedReader br = Files.newBufferedReader(path, StandardCharsets.UTF_8);) {
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while ((line = br.readLine()) != null) {
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System.out.println(line);
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}
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}
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}
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/**
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* 自古以来
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*/
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@Test
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public void test7() {
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File file = new File("/Users/darcy/wdbyte/log.txt");
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try (Scanner sc = new Scanner(new FileReader(file))) {
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while (sc.hasNextLine()) {
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String line = sc.nextLine();
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System.out.println(line);
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}
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} catch (FileNotFoundException e) {
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throw new RuntimeException(e);
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}
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}
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/**
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* 自古以来
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*/
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@Test
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public void test8() {
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File file = new File("/Users/darcy/wdbyte/log.txt");
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try (FileInputStream fis = new FileInputStream(file);
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BufferedInputStream bis = new BufferedInputStream(fis);) {
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StringBuilder content = new StringBuilder();
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int data;
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while ((data = bis.read()) != -1) {
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content.append((char)data);
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}
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System.out.println(content.toString());
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} catch (IOException e) {
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e.printStackTrace();
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}
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}
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}

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