Java know how much (67) character-oriented input stream

Character streams are optimized for characters, thus providing some useful character-oriented features, and the source or target of a character stream is usually a text file. Reader and writer are the parent classes of all character streams in the java.io package. Because they are abstract classes, you should use their subclasses to create entity objects that use objects to handle related read and write operations. The subclasses of reader and writer can be divided into two categories: one to read data from a data source or to write data to a destination (called a node stream), and another to perform some sort of processing (called a process flow) on the data.

Character-oriented input stream classes are subclasses of reader, as shown in class hierarchy 10-2.

Figure 10-2 class hierarchy diagram for reader

Table 10-1 lists the main subclasses and descriptions of Reader.

Table 10-1 main subclasses of Reader

class name	function Description
CharArrayReader	Input stream read from a character array
BufferedReader	Buffered input character stream
Pipedreader	Input piping
InputStreamReader	The input stream that converts bytes to characters
FilterReader	Filter input Stream
StringReader	Input stream read from a string
LineNumberReader	Append line numbers for input data
Pushbackreader	Returns a character and puts this byte back into the input stream
FileReader	Input stream read from file

The methods provided by Reader, as shown in table 10-2, can be used to obtain bit data within the stream.

Table 10-2 Common methods of Reader

Method	function Description
void Close ()	Close the input stream
void Mark ()	Mark the current position of the input stream
Boolean marksupported ()	Test whether the input stream supports mark
int read ()	Reads a character from the input stream
int read (char[] ch)	Reading an array of characters from an input stream
int read (char[] ch, int off, int len)	Read Len long characters from the input stream into CH
Boolean Ready ()	Whether the test flow can read
void Reset ()	Reposition input Stream
Long Skip (long N)	Skips n characters within a stream

Reading files using the FileReader class

The FileReader class is a subclass of the reader subclass InputStreamReader class, so the FileReader class can use either the reader class's method or the InputStreamReader class's method to create the object.

When you use the FileReader class to read a file, you must first call the FileReader () construction method to create an object of the FileReader class, and then call the Read () method. The format of the FileReader constructor method is:
Public FileReader (String name); Creates a readable input stream object based on the file name

Example 10-1 uses the FileReader class to read the contents of a plain text file (view the source code).

Running result 10-3 shows:

Figure 10-3 Example 10_1 running results (output is the contents of the file Ep10_1.txt)

It is important to note that Java treats a Chinese or English letter as a character, a carriage return or a newline as two characters.

Reading files using the BufferedReader class

The BufferedReader class is used to read the data in the buffer. You must create a FileReader class object when you use it, and then create an object of the BufferedReader class with that object as a parameter. The BufferedReader class has two construction methods in the form of:
Public BufferedReader (Reader in); Creating a buffer character input stream
Public BufferedReader (Reader in,int size); Create an input stream and set the buffer size

Example 10-2 uses the BufferedReader class to read the contents of a plain text file (view the source code).

Running result 10-4 shows:

Figure 10-4 Example 10_2 running results

It is important to note that when executing the read () or write () method, the system throws a IOException exception due to an IO error, the statement that performs the read-write operation needs to be included in the try block, and the corresponding catch block is used to handle the possible exception.

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Java know how much (67) character-oriented input stream