全面了解java byte数组与文件读写

全面了解java byte数组与文件读写

import java.io.bytearrayoutputstream;
import java.io.file;
import java.io.fileinputstream;
import java.io.fileoutputstream;
import java.io.ioexception;

public class filehelper {
<span style="white-space:pre">  </span>//第一种获取文件内容方式
  public byte[] getcontent(string filepath) throws ioexception {
    file file = new file(filepath);

    long filesize = file.length();
    if (filesize > integer.max_value) {
      system.out.println("file too big...");
      return null;
    }

    fileinputstream fi = new fileinputstream(file);

    byte[] buffer = new byte[(int) filesize];

    int offset = 0;

    int numread = 0;

    while (offset < buffer.length

    && (numread = fi.read(buffer, offset, buffer.length - offset)) >= 0) {

      offset += numread;

    }

    // 确保所有数据均被读取

    if (offset != buffer.length) {

      throw new ioexception("could not completely read file "
          + file.getname());

    }

    fi.close();

    return buffer;
  }
  
  //第二种获取文件内容方式
  public byte[] getcontent2(string filepath) throws ioexception
  {
    fileinputstream in=new fileinputstream(filepath);
    
    bytearrayoutputstream out=new bytearrayoutputstream(1024);
    
    system.out.println("bytes available:"+in.available());
    
    byte[] temp=new byte[1024];
    
    int size=0;
    
    while((size=in.read(temp))!=-1)
    {
      out.write(temp,0,size);
    }
    
    in.close();
    
    byte[] bytes=out.tobytearray();
    system.out.println("bytes size got is:"+bytes.length);
    
    return bytes;
  }
    //将byte数组写入文件
  public void createfile(string path, byte[] content) throws ioexception {

    fileoutputstream fos = new fileoutputstream(path);

    fos.write(content);
    fos.close();
  }

}

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