Java中BufferedReader与BufferedWriter类的使用示例

import java.io.BufferedReader;
import java.io.ByteArrayInputStream;
import java.io.File;
import java.io.InputStream;
import java.io.FileReader;
import java.io.IOException;
import java.io.FileNotFoundException;
import java.lang.SecurityException;

public class BufferedReaderTest {

  private static final int LEN = 5;

  public static void main(String[] args) {
    testBufferedReader() ;
  }

  /**
   * BufferedReader的API测试函数
   */
  private static void testBufferedReader() {

    // 创建BufferedReader字符流，内容是ArrayLetters数组
    try {
      File file = new File("bufferedreader.txt");
      BufferedReader in =
         new BufferedReader(
           new FileReader(file));

      // 从字符流中读取5个字符。“abcde”
      for (int i=0; i<LEN; i++) {
        // 若能继续读取下一个字符，则读取下一个字符
        if (in.ready()) {
          // 读取“字符流的下一个字符”
          int tmp = in.read();
          System.out.printf("%d : %c\n", i, tmp);
        }
      }

      // 若“该字符流”不支持标记功能，则直接退出
      if (!in.markSupported()) {
        System.out.println("make not supported!");
        return ;
      }

      // 标记“当前索引位置”，即标记第6个位置的元素--“f”
      // 1024对应marklimit
      in.mark(1024);

      // 跳过22个字符。
      in.skip(22);

      // 读取5个字符
      char[] buf = new char[LEN];
      in.read(buf, 0, LEN);
      System.out.printf("buf=%s\n", String.valueOf(buf));
      // 读取该行剩余的数据
      System.out.printf("readLine=%s\n", in.readLine());

      // 重置“输入流的索引”为mark()所标记的位置，即重置到“f”处。
      in.reset();
      // 从“重置后的字符流”中读取5个字符到buf中。即读取“fghij”
      in.read(buf, 0, LEN);
      System.out.printf("buf=%s\n", String.valueOf(buf));

      in.close();
    } catch (FileNotFoundException e) {
      e.printStackTrace();
    } catch (SecurityException e) {
      e.printStackTrace();
    } catch (IOException e) {
      e.printStackTrace();
    }
  }
}

abcdefghijklmnopqrstuvwxyz
0123456789
ABCDEFGHIJKLMNOPQRSTUVWXYZ

0 : a
1 : b
2 : c
3 : d
4 : e
buf=01234
readLine=56789
buf=fghij

import java.io.BufferedWriter;
import java.io.File;
import java.io.OutputStream;
import java.io.FileWriter;
import java.io.IOException;
import java.io.FileNotFoundException;
import java.lang.SecurityException;
import java.util.Scanner;

public class BufferedWriterTest {

  private static final int LEN = 5;
  // 对应英文字母“abcdefghijklmnopqrstuvwxyz”
  //private static final char[] ArrayLetters = "abcdefghijklmnopqrstuvwxyz";
  private static final char[] ArrayLetters = new char[] {'a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z'};

  public static void main(String[] args) {
    testBufferedWriter() ;
  }

  /**
   * BufferedWriter的API测试函数
   */
  private static void testBufferedWriter() {

    // 创建“文件输出流”对应的BufferedWriter
    // 它对应缓冲区的大小是16，即缓冲区的数据>=16时，会自动将缓冲区的内容写入到输出流。
    try {
      File file = new File("bufferwriter.txt");
      BufferedWriter out =
         new BufferedWriter(
           new FileWriter(file));

      // 将ArrayLetters数组的前10个字符写入到输出流中
      out.write(ArrayLetters, 0, 10);
      // 将“换行符\n”写入到输出流中
      out.write('\n');

      out.flush();
      //readUserInput() ;

      out.close();
    } catch (FileNotFoundException e) {
      e.printStackTrace();
    } catch (SecurityException e) {
      e.printStackTrace();
    } catch (IOException e) {
      e.printStackTrace();
    }
  }

  /**
   * 读取用户输入
   */
  private static void readUserInput() {
    System.out.println("please input a text:");
    Scanner reader=new Scanner(System.in);
    // 等待一个输入
    String str = reader.next();
    System.out.printf("the input is : %s\n", str);
  }
}