what is io
Disk IO (Input/Output) refers to the data transmission process between the computer and external storage devices (such as hard disk, U disk, etc.). In a computer, data needs to be read from memory to disk for storage, or read from disk to memory for processing, which requires disk IO operations.
Disk IO usually consists of two operations: read and write. A read operation is to read data from disk into memory, and a write operation is to write data from memory to disk. Disk IO operations are slower because disk reads and writes are much slower than memory. Therefore, when writing a program, it is necessary to reduce disk IO operations as much as possible to improve the execution efficiency of the program.
In Java, you can use input and output streams (InputStream/OutputStream) for disk IO operations. For example, you can use a FileInputStream to read a file on disk and a FileOutputStream to write data to a file on disk. In addition, Java also provides buffered input and output streams (BufferedInputStream/BufferedOutputStream) to improve the efficiency of disk IO operations.
What are the Java io streams
In Java, disk IO is implemented through input and output streams (InputStream/OutputStream). Java provides a variety of input and output stream classes that can be used to read and write different types of data.
FileInputStream/FileOutputStream
FileInputStream and FileOutputStream are the most basic input and output stream classes for reading and writing binary data, usually for reading and writing files.
Sample code:
FileReader and FileWriter are input and output stream classes for reading and writing character data, usually for reading and writing text files.
BufferedReader and BufferedWriter are cache-based input and output stream classes that can improve the efficiency of disk IO operations. They can encapsulate the underlying input and output streams into buffered input and output streams, thereby reducing the number of IO operations on the disk and improving the efficiency of reading and writing data.
ObjectInputStream and ObjectOutputStream are input and output stream classes for reading and writing Java objects, which can serialize Java objects to disk or deserialize Java objects from disk.
In short, in Java, disk IO is implemented through input and output streams. Different types of input and output stream classes can be selected for read and write operations according to needs, and cached input and output streams are used as much as possible to improve read and write efficiency.
Advantages and disadvantages of disk io
advantage:
Data persistence: The disk is a non-volatile storage device that can save data for a long time and will not be lost even if the power is turned off.
Large storage capacity: The storage capacity of the disk is usually much larger than that of the memory, which can store a large amount of data.
High reliability: The data storage of the disk adopts a redundancy mechanism, which can ensure the reliability and integrity of the data.
shortcoming:
Slow speed: Compared with other storage devices such as memory, the read and write speed of the disk is slow, which will affect the performance of the program.
IO operations are time-consuming: Disk IO operations usually take a long time, which will cause program blockage and affect user experience.
Disk Failure: Disks are mechanical storage devices that are susceptible to things like physical damage and disk failure, making data unreadable or lost.
To sum up, the disk IO operation is a persistent storage method that can save data for a long time, but due to the disadvantages of slow read and write speeds and time-consuming IO operations, it needs to be reasonably optimized during program design.