Java Interview – Java basic IO streams

Master the inheritance system of InputStream, OutputStream, Reader, and Writer.

1. What is a Bit, what is a Byte, and what is a Char? How long are they

The answer

Byte is the smallest unit of data that a computer can operate on. The value consists of eight bits (-128-127). Char is the smallest unit of data that a user can read and write. In Java, the value consists of 16 bits (0 to 65535). A bit is the smallest unit that a computer can recognize only 0 or 1. 8 bytes are the characters shown to the computerCopy the code

2. What are streams, which are divided into two streams according to the unit of transmission, and what is their parent stream called the transmission of data

The answer

InputStream OutputStream Character stream: Reader WriterCopy the code

3. The flow can be divided into two types according to the direction of transmission

The answer

Input and output relative to program InputStream InputStream OutputStream OutputStreamCopy the code

4. According to the realization of functions, which two kinds are divided into, respectively illustrate

The answer

Node stream, processing stream Node stream: OutputStream Processing stream: OutputStreamWriterCopy the code

5. What stream is BufferedReader, what is it mainly used for, and what are the classic methods in it

The answer

A buffered stream in a processing stream that stores the read in memory, with the readLine () methodCopy the code

6. What is a node stream and what is a process stream, what are their uses, and what are the characteristics of the creation of a process stream

The answer

A node stream is directly connected to a data source and is used for input or output processing streams: the constructor of a node stream must pass in a subclass of the node stream to process on top of it, extending some of its functionalityCopy the code

7. If I want to do a lot of byte stream reading from hard disk, which stream should I use? Why

The answer

BufferedInputStream Using buffered streams can reduce damage to your hard driveCopy the code

8. If I want to print different types of data to a data source, which stream is the most suitable? Why

The answer

Printwriter can print a variety of data typesCopy the code

9. How to change the output of our console to an output file? What is this technique called

The answer

SetOut (printWriter,printStream) redirectsCopy the code

10. When do you use serializable in your Java code? How to implement Java serialization?

The answer

To write an object to or read from a data source using Serializable, you need to implement the Serializable interfaceCopy the code

11. How to convert an output byte stream to an output character stream and say its steps

The answer

New OutputStreamWriter (New FileOutputStream (File File));Copy the code

12. Which two streams are used to output or read data and strings, including primitive types, sequentially to or from the data source

The answer

DataInputStream DataOutputStream
Copy the code

13. Which two streams are used to write an object to or read from a data source

The answer

ObjectInputStream ObjectOutputStream
Copy the code

14. What is object serialization, what is deserialization, and what needs to be done to realize object serialization

The answer

Object serialization, the object in binary form saved on the hard disk deserialization; Convert binary files into objects to read implement serialIZABLE interface do not want to put fields on the hard disk add transientCopy the code

15. Which keyword should be used if you don’t want to store a field’s data on hard disk during object serialization?

The answer

Transient keywordCopy the code

16. When implementing serialization interface, a serialVersionUID field is generated. What is it called and what is it used for

The answer

Is the version number, and you want to keep the same version number to serialize in case of serialization errorsCopy the code

17. What does read() in InputStream return? What does read(byte[] data) mean

The answer

Read (byte [] data) Stores the read bytes in this array and returns the number of parameters in the array. Read byte Read byte character Read characterCopy the code

Write (byte b[], int off, int len) OutputStream

The answer

Write passes the specified Byte to the data source. Byte B [] is the Byte array. B [off] is the first character passed in. B [off+len-1] is the last character passed inCopy the code

19. Streams usually do not need to be closed. If they are closed, what method is used?

The answer

Once opened, a stream must be closed. A processing stream called using the close method ina finally statement block (finally statements must be executed) closes the processing stream. Multiple streams calling each other close only the outermost streamCopy the code

20. All flows in Java can be divided into several broad categories, what are their names, and what do they stand for

The answer

Byte InputStream byte OutputStream OutputStream character InputStream Reader character OutputStream Writer all streams are subclasses of the four streamsCopy the code

21. Describe common I/O streams

The answer

InputStream,OutputStream,FileInputStream,FileOutputStream,BufferedInputStream,BufferedOutputStreamReader,WriterBufferedR eader,BufferedWriterCopy the code

22. How does an IO stream read files?

The answer

Get the File path using the File object, add the File to the stream Reader, process the Reader using the BufferedReader stream, define a string, and loop through the File. File File = new File("d:/spring.txt"); try {Reader reader = new FileReader(file); BufferedReader buffered = new BufferedReader(reader); String data = null; while((data = buffered.readLine())! =null){System.out.println(data); }} catch (FileNotFoundException e) {e.printStackTrace(); } catch (IOException e) {e.printStackTrace(); }Copy the code

23. Tell me what you understand about IO streams

The answer

Io streams are mainly used to deal with input and output problems. The commonly used I/O streams include InputStream, OutputStream, Reader, Writer, and so onCopy the code

JAVA IO streams and readLine methods

The answer

Java IO streams handle input/output problems, and readLine is a method in BufferedReader that reads a line.Copy the code

25. What is used to dynamically write objects to disk, and what interfaces are to be implemented.

The answer

ObjectInputStream requires the Serializable interface to be implementedCopy the code

26.FileInputStream is created in several different ways.

The answer

A FileInputStream is a subclass of InputStream. By definition of the interface, a subclass can create a FileInputStream.Copy the code

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