[Java] java_IO向文件中写入和读取内容代码实例

package stream;
 
import java.io.file;
import java.io.filenotfoundexception;
import java.io.fileoutputstream;
import java.io.ioexception;
import java.io.outputstream;
 
 
public class outstreamdemo01 {
  public static void main(string[] args) {
    //定义文件路径，没有该文件会自动创建，如果路径有文件夹，一定要有，不会自动创建文件夹
    string filename = "e:"+file.separator+"a"+file.separator+"b.txt";
    file file = new file(filename);
    string str = "这些都将写入文件中";
    byte[] b = str.getbytes();  //将字符串转换成字节数
    outputstream out = null;
    try {
      out = new fileoutputstream(file);   //实例化outpurstream
    }catch(filenotfoundexception e){
      e.printstacktrace();
    }
    
    //写入
    try {
      out.write(b);     //写入
      out.close();    //关闭
    } catch (ioexception e) {
      // todo auto-generated catch block
      e.printstacktrace();
    }
  }
}

package stream;
import java.io.*;;
public class inputstreamdemo01 {
  public static void main(string[] args) {
    file file = new file("e:"+file.separator+"a"+file.separator+"b.txt");
    byte[] b = new byte[(int)file.length()];//定义byte字节的长度
    inputstream in = null;
    int len = 0;
    try {     //处理异常
      in = new fileinputstream(file);   //实例化fileinputstream类
    } catch (filenotfoundexception e) {
      // todo auto-generated catch block
      e.printstacktrace();    //输出异常
    }
    try {
      len = in.read(b);     //读取指定文件的内容
      in.close();
    } catch (ioexception e) {
      // todo auto-generated catch block
      e.printstacktrace();
    }
    system.out.println(new string(b,0,len));//将字节数组转化成字符串输出指定文件从0开始到len字节结束
  }
}