Java之输入与输出

过程中发生的所有异常都是IOException的子类。

字节流

文件输入流

import java.io.*;

public class ByteReader {
    public static void main(String[] arguments) {
        try (
            FileInputStream file = new
                FileInputStream("save.gif")
            ) {

            boolean eof = false;
            int count = 0;
            while (!eof) {
                int input = file.read();
                System.out.print(input + " ");
                if (input == -1)
                    eof = true;
                else
                    count++;
            }
            file.close();
            System.out.println("\nBytes read: " + count);
        } catch (IOException e) {
            System.out.println("Error -- " + e.toString());
        }
    }
}

文件输出流

import java.io.*;

public class ByteWriter {
    public static void main(String[] arguments) {
        int[] data = { 71, 73, 70, 56, 57, 97, 13, 0, 12, 0, 145, 0,
            0, 255, 255, 255, 255, 255, 0, 0, 0, 0, 0, 0, 0, 44, 0,
            0, 0, 0, 13, 0, 12, 0, 0, 2, 38, 132, 45, 121, 11, 25,
            175, 150, 120, 20, 162, 132, 51, 110, 106, 239, 22, 8,
            160, 56, 137, 96, 72, 77, 33, 130, 86, 37, 219, 182, 230,
            137, 89, 82, 181, 50, 220, 103, 20, 0, 59 };
        try (FileOutputStream file = new
            FileOutputStream("pic.gif")) {

            for (int i = 0; i < data.length; i++) {
                file.write(data[i]);
            }
            file.close();
        } catch (IOException e) {
            System.out.println("Error -- " + e.toString());
        }
    }
}

字符流

读取文本文件

例一：

import java.io.*;
public class FileCopy {
	public static void main(String args[]) throws IOException{
	FileReader f1;
	FileWriter f2;
	f1=new FileReader("FileCopy.java");
	f2=new FileWriter("acopy_of_java_file.java");
	int temp;
	while((temp=f1.read())!=-1);
	f2.write(temp);
	f1.close(); f2.close(); }
	public FileCopy() { }
}

例二：

import java.io.*;

public class SourceReader {
    public static void main(String[] arguments) {
        try (
            FileReader file = new
                FileReader("SourceReader.java");
            BufferedReader buff = new	//这是讲读取的字符存储到缓冲区，以提高效率。
                BufferedReader(file)) {

            boolean eof = false;
            while (!eof) {
                String line = buff.readLine();
                if (line == null) {
                    eof = true;
                } else {
                    System.out.println(line);
                }
            }
            buff.close();
        } catch (IOException e) {
            System.out.println("Error -- " + e.toString());
        }
    }
}