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 {
  //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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