Java IO data operation stream, object serialization, compressed stream code parsing

Data operation flow

In the IO package, two platform independent data operation flows are provided:

Data input stream

Data output stream

Usually, the data output stream will output the data in a certain format, and then read the data in a certain format through the data input stream

The dataoutputstream interface defines a series of writexxx() operations, which can write data of various data types.

Example: write and read data using data operation stream

Object serialization

Object serialization is a method to turn an object into a binary data stream. Object transmission or storage can be easily realized through object serialization.

If a class wants to support initialization, it must implement Java io. Serilizable interface. The interface is defined as follows:

publicinterfaceSerilizable{}

There is no method in this interface, so this class belongs to a marked interface, indicating that the class implementing this interface has some capability.

1. Object serialization and deserialization

2.serialVersionUID

A serialVersionUID constant is introduced in the serialization operation to verify the consistency of the version. During deserialization, the JVM will compare the serialVersionUID in the transmitted byte stream with the serialVersionUID of the local corresponding class. If it is the same, it is considered to be consistent and can be deserialized, Otherwise, an exception with inconsistent serialization version will occur.

3. Object output stream: objectoutputstream

To output an object, you must use the objectoutputstream class, which is defined as follows

If a property in an object does not want to be serialized, it can be declared using the transient keyword.

4. Object input stream: objectinputstream

6. Serialize a set of objects

Object output only provides the output operation of one object (writeobject (objectobj)), but does not provide the output of multiple objects. If you want to serialize multiple objects now, you can use the object array. Because the array is a reference data type, you can directly use the object type to receive.

The array can store a limited number of objects, so you can use the class set for serialization.

Compressed flow

In Java, in order to reduce the amount of data during transmission, compressed streams are also provided. Files or folders can be compressed into zip, jar, gzip and other formats.

This stream is rarely used, so it is only briefly introduced.

summary

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