BytesWritable 的copyBytes和getBytes的区别

本文深入探讨了BytesWritable在Hadoop中用于数据存储的copyBytes和getBytes两个方法的差异。copyBytes()用于复制数据,而getBytes()则返回内部存储的字节数组。了解这两个方法的不同对于优化Hadoop应用程序的性能至关重要。

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BytesWritable value = new BytesWritable();

BytesWritable不能作为mapreduce中的key或者value,与ByteWritable不同。

1,BytesWritable.tobyte()//将ByteWritable类型的数据转换为十六进制对,并以空格分开;

2,BytesWritable.set(byte[] newData,int offset,int length);//将值设置为给定的字节范围的副本

3,BytesWritable.copyBytes()//获得对象的byte[]类型全部数据:Get a copy of the bytes that is exactly the length of the data. See getBytes() for faster access to the underlying array.

4,BytesWritable.getBytes()//**Get the data backing the BytesWritable. Please use copyBytes() if you need the returned array to be precisely the length of the data.**
Modifier and TypeMethod and Description
byte[]copyBytes():Get a copy of the bytes that is exactly the length of the data.
booleanequals(Object right_obj):Are the two byte sequences equal?
byte[]get():Deprecated. Use getBytes() instead.
byte[]getBytes():Get the data backing the BytesWritable.
intgetCapacity():Get the capacity, which is the maximum size that could handled without resizing the backing storage.
intgetLength():Get the current size of the buffer.
intgetSize():Deprecated.Use getLength() instead.
inthashCode():Return a hash of the bytes returned from {#getBytes()}.
voidreadFields(DataInput in):Deserialize the fields of this object from in.
voidset(byte[] newData, int offset, int length):Set the value to a copy of the given byte range
voidset(BytesWritable newData):Set the BytesWritable to the contents of the given newData.
voidsetCapacity(int new_cap):Change the capacity of the backing storage.
voidsetSize(int size):Change the size of the buffer.
StringtoString():Generate the stream of bytes as hex pairs separated by ’ '.
voidwrite(DataOutput out):Serialize the fields of this object to out.
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