java中IO流代码实例分析

最新推荐文章于 2023-10-15 19:18:43 发布

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最新推荐文章于 2023-10-15 19:18:43 发布

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本文介绍了一个使用Java进行文件操作的示例程序，包括文件的读取、写入、删除及替换内容等基本功能，并演示了如何复制文件。通过具体代码展示了如何利用FileReader、FileWriter、BufferedReader和BufferedWriter等类实现对文件的操作。

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import java.io.BufferedWriter;

import java.io.File;

import java.io.FileInputStream;

import java.io.FileOutputStream;

import java.io.FileReader;

import java.io.FileWriter;

import java.io.IOException;

import java.io.InputStream;

import org.junit.Test;

public class TestStream {

// 读取文件中字符

@Test

public void testRead() throws IOException {

String path = "read.txt";

FileReader read = new FileReader(path);

BufferedReader reader = new BufferedReader(read);

while (reader.readLine() != null) {

String s = reader.readLine();

System.err.println(s);

}

reader.close();

}

// 写入字符到文件

@Test

public void testWrite() throws IOException {

String path = "write.txt";

FileWriter write = new FileWriter(path);

BufferedWriter writer = new BufferedWriter(write);

char[] buffer = new char[1024];

for (int i = 0; i < 1024; i++) {

if ((char) 'a' + i > Character.MAX_VALUE) {

buffer[i] = 'z'; System.err.println(1);

} else {

buffer[i] = (char) ('a' + i);

}

writer.write(buffer);

writer.close();

}

// 删除文件内容

@Test

public void testDelete() throws IOException {

String path = "write.txt";

FileWriter write = new FileWriter(path);

BufferedWriter writer = new BufferedWriter(write);

StringBuffer buffer = new StringBuffer();

writer.write(buffer.toString());

writer.close();

}

// 替换内容

@Test

public void testDeleteAndReplace() throws IOException {

String path = "write.txt";

FileWriter write = new FileWriter(path);

BufferedWriter writer = new BufferedWriter(write);

int i = 0;

while (++i < 100) {

StringBuffer buffer = new StringBuffer();

buffer.append(Math.random());

writer.write(buffer.toString() + "\r\n");

}

writer.close();

}

// 拷贝一个文件内容到另一个文件

@Test

public void copyFile(String oldPath, String newPath) {

try {

int byteread = 0;

File oldfile = new File(oldPath);

if (oldfile.exists())

}

//文件存在时

InputStream inStream = new FileInputStream(oldPath);

//读入原文件

FileOutputStream fs = new FileOutputStream(newPath);

byte[] buffer = new byte[100];

while ((byteread = inStream.read(buffer)) != -1) {

fs.write(buffer, 0, byteread);

}

inStream.close();

fs.close();

}

} catch (Exception e) {

e.printStackTrace();

}

//读取字符流

@Test

public static void testReadByte() {

String path = "write.txt";

File file = new File(path);

InputStream in = null;

try {

// 一次读一个字节

in = new FileInputStream(file);

int tempbyte;

while ((tempbyte = in.read()) != -1) {

System.out.write(tempbyte);

}

in.close();

} catch (IOException e) {

e.printStackTrace();

return;

}

try {

// 一次读多个字节

byte[] tempbytes = new byte[100];

int byteread = 0;

in = new FileInputStream(path);

while ((byteread = in.read(tempbytes)) != -1) {

System.out.write(tempbytes, 0, byteread);

}

} catch (Exception e1) {

e1.printStackTrace();

} finally {

if (in != null) {

try {

in.close();

} catch (IOException e1) {

}