【Java复习巩固 Day7】输入/输出

File类

如果希望在程序中操作文件和目录，都可以通过File类来完成

package day7;

import java.io.File;
import java.io.IOException;

public class FileTest {
    public static void main(String[] args) throws IOException {
        File file = new File(".");
        // 获取文件名
        System.out.println(file.getName());
        // 获取绝对路径
        System.out.println(file.getAbsolutePath());
        // 列出当前路径下所有的文件
        String[] fileList = file.list();
        if (fileList != null) {
            for (String fileName : fileList) {
                System.out.println(fileName);
            }
        }
    }
}

eg：递归遍历目录

package day7;

import java.io.File;
import java.util.Scanner;

/**
 * 递归遍历目录
 */
public class FileWalk {

    public static void walk(String path) {
        File file = new File(path);
        File[] files = file.listFiles();
        if (files != null) {
            for (File file1 : files) {
                if (file1.isFile()) {
                    System.out.println(file1.getName());
                } else if (file1.isDirectory()) {
                    walk(file1.getPath());
                }
            }
        }
    }

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        String path = scanner.next();
        walk(path);
    }
}

字节流和字符流

字节流操作的数据单元是字节，字符流操作的单元是字符

InputStream和Reader

package day7;

import java.io.FileInputStream;
import java.io.IOException;

public class FileInputStreamTest {
    public static void main(String[] args) throws IOException {
        FileInputStream inputStream = new FileInputStream("properties.txt");
        byte[] bytes = new byte[1024];
        int len;
        while ((len = inputStream.read(bytes)) != -1) {
            System.out.print(new String(bytes, 0, len));
        }
        inputStream.close();
    }
}

package day7;

import java.io.FileReader;
import java.io.IOException;

public class FileReaderTest {
    public static void main(String[] args) {
        try(FileReader fileReader = new FileReader("properties.txt")) {
            char[] chars = new char[32];
            int len;
            while ((len=fileReader.read(chars)) != -1) {
                System.out.print(new String(chars, 0, len));
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

OutputStream和Writer

package day7;

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;

/**
 * 文件复制
 */
public class FileOutputStreamTest {
    public static void main(String[] args) throws IOException {
        // 创建字节输入流
        FileInputStream fileInputStream = new FileInputStream("properties.txt");
        // 创建字节输出流
        FileOutputStream fileOutputStream = new FileOutputStream("properties.bak.txt");
        byte[] bytes = new byte[1024];
        int len;
        while ((len = fileInputStream.read(bytes)) != -1) {
            fileOutputStream.write(bytes, 0, len);
        }
        fileOutputStream.close();
        fileInputStream.close();
    }
}

package day7;

import java.io.FileWriter;
import java.io.IOException;

public class FileWriterTest {
    public static void main(String[] args) throws IOException {
        String string = "学习贯彻";
        FileWriter fileWriter = new FileWriter("text.txt");
        fileWriter.write(string);
        fileWriter.close();
    }
}

如果进行输入输出的内容是文本内容，则应该考虑使用字符流
如果进行输入输出的内容是二进制内容，则应该考虑使用字节流

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