Java入门——day55 - 戈瑾

一、字节输入、输出流

1.InputStream读取文件

 1 import java.io.File;
 2 import java.io.FileInputStream;
 3 import java.io.InputStream;
 4 public class Demo {
 5     public static void main(String[] args) throws Exception {
 6         File file = new File("D://测试文件.txt");
 7         InputStream in = new FileInputStream(file);
 8         int fileLength = (int) file.length();
 9         byte b[] = new byte[fileLength];
10         in.read(b);
11         in.close();
12         System.out.println("读取的内容是：" + new String(b));
13     }
14 }

2.OutputStream写入文件

 1 import java.io.File;
 2 import java.io.FileOutputStream;
 3 import java.io.OutputStream;
 4 public class Demo {
 5     public static void main(String[] args) throws Exception {
 6         File file = new File("D://测试文件.txt");
 7         OutputStream out=new FileOutputStream(file);
 8         String str="Java你好！";
 9         byte b[]=str.getBytes();
10         out.write(b);
11         out.close();
12     }
13 }

二、字符输入、输出流

1.Reader读取文件

一起读取：

 1 import java.io.File;
 2 import java.io.FileReader;
 3 import java.io.Reader;
 4 public class Demo {
 5     public static void main(String[] args) throws Exception {
 6         File file = new File("D://测试文件.txt");
 7         Reader reader=new FileReader(file);
 8         char c[]=new char[1024]; //字符数组
 9         int len=reader.read(c);
10         reader.close();
11         System.out.println("读取的内容是："+new String(c,0,len));
12     }
13 }

逐个读取：

 1 import java.io.File;
 2 import java.io.FileReader;
 3 import java.io.Reader;
 4 public class Demo {
 5     public static void main(String[] args) throws Exception {
 6         File file = new File("D://测试文件.txt");
 7         Reader reader=new FileReader(file);
 8         char c[]=new char[1024]; //字符数组
 9         int temp=0;
10         int len=0;
11         while((temp=reader.read())!=-1) {
12             c[len++]=(char)temp;
13         }
14         reader.close();
15         System.out.println("读取的内容是："+new String(c,0,len));
16     }
17 }

2.Writer写入文件

以覆盖的形式：

 1 import java.io.File;
 2 import java.io.FileWriter;
 3 import java.io.Writer;
 4 public class Demo {
 5     public static void main(String[] args) throws Exception {
 6         File file = new File("D://测试文件.txt");
 7         Writer out=new FileWriter(file);
 8         String str="我爱Java";
 9         out.write(str);  //将字符串写入输出流
10         out.close();
11     }
12 }

以追加的形式：

 1 import java.io.File;
 2 import java.io.FileWriter;
 3 import java.io.Writer;
 4 public class Demo {
 5     public static void main(String[] args) throws Exception {
 6         File file = new File("D://测试文件.txt");
 7         Writer out=new FileWriter(file,true);
 8         String str="，你也爱Java";
 9         out.write(str);  //将字符串写入输出流
10         out.close();
11     }
12 }

posted on 2020-08-29 17:31 戈瑾阅读(190) 评论(0) 收藏举报

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