CharBuffer read() methods in Java with Examples
The read() method of java.nio.CharBuffer Class is used to read characters into the specified character buffer. The buffer is used as a repository of characters as-is: the only changes made are the results of a put operation. No flipping or rewinding of the buffer is performed.
Syntax:
public int read(CharBuffer target)
Parameter: This method takes the buffer to read characters into.
Return Value: This method returns the number of characters added to the buffer, or -1 if this source of characters is at its end.
Exception: This method throws following exception:-
- IOException – if an I/O error occurs
- NullPointerException – if target is null
- ReadOnlyBufferException – if target is a read only buffer
Below are the examples to illustrate the read() method:
Examples 1:
// Java program to demonstrate // read() method import java.nio.*; import java.util.*; import java.io.IOException; public class GFG { public static void main(String[] args) { try { // Declare and initialize the char array char [] cb1 = { 'x' , 'y' , 'z' }; char [] cb2 = { 'a' , 'b' , 'c' , 'd' , 'e' }; // wrap the char array into CharBuffer // using wrap() method CharBuffer charBuffer1 = CharBuffer.wrap(cb1); // wrap the char array into CharBuffer // using wrap() method CharBuffer charBuffer2 = CharBuffer.wrap(cb2); // print the byte buffer System.out.println( "CharBuffer Before operation is: " + Arrays.toString( charBuffer1.array()) + "\nTarget Charbuffer: " + Arrays.toString( charBuffer2.array())); // Get the value of the number of Character // read from the charBuffer // using read() method int value = charBuffer1 .read(charBuffer2); // print the byte buffer System.out.println( "\nCharBuffer After operation is: " + Arrays.toString( charBuffer1.array()) + "\nTarget Charbuffer: " + Arrays.toString( charBuffer2.array()) + "\nno of value changed: " + value); } catch (IOException e) { System.out.println( "an I/O error occurs" ); System.out.println( "Exception throws: " + e); } catch (NullPointerException e) { System.out.println( "target charbuffer is null" ); System.out.println( "Exception throws: " + e); } catch (ReadOnlyBufferException e) { System.out.println( "target is a read only buffer" ); System.out.println( "Exception throws: " + e); } } } |
CharBuffer Before operation is: [x, y, z] Target Charbuffer: [a, b, c, d, e] CharBuffer After operation is: [x, y, z] Target Charbuffer: [x, y, z, d, e] no of value changed: 3
Examples 2: For NullPointerException
// Java program to demonstrate // read() method import java.nio.*; import java.util.*; import java.io.IOException; public class GFG { public static void main(String[] args) { try { // Declare and initialize the char array char [] cb1 = { 'x' , 'y' , 'z' }; // wrap the char array into CharBuffer // using wrap() method CharBuffer charBuffer1 = CharBuffer.wrap(cb1); // print the byte buffer System.out.println( "CharBuffer Before operation is: " + Arrays.toString( charBuffer1.array())); // Get the value of number of Character // read from the charBuffer // using read() method int value = charBuffer1.read( null ); } catch (IOException e) { System.out.println( "\nan I/O error occurs" ); System.out.println( "Exception throws: " + e); } catch (NullPointerException e) { System.out.println( "\ntarget charbuffer is null" ); System.out.println( "Exception throws: " + e); } catch (ReadOnlyBufferException e) { System.out.println( "\ntarget is a read only buffer" ); System.out.println( "Exception throws: " + e); } } } |
CharBuffer Before operation is: [x, y, z] target charbuffer is null Exception throws: java.lang.NullPointerException
Examples 3: For ReadOnlyBufferException
// Java program to demonstrate // read() method import java.nio.*; import java.util.*; import java.io.IOException; public class GFG { public static void main(String[] args) { try { // Declare and initialize the char array char [] cb1 = { 'x' , 'y' , 'z' }; char [] cb2 = { 'a' , 'b' , 'c' , 'd' , 'e' }; // wrap the char array into CharBuffer // using wrap() method CharBuffer charBuffer1 = CharBuffer.wrap(cb1); // wrap the char array into CharBuffer // using wrap() method CharBuffer charBuffer2 = CharBuffer.wrap(cb2); // print the byte buffer System.out.println( "CharBuffer Before operation is: " + Arrays.toString( charBuffer1.array()) + "\nTarget Charbuffer: " + Arrays.toString( charBuffer2.array())); // converting Charbuffer to readonlybuff CharBuffer readonlybuff = charBuffer2.asReadOnlyBuffer(); // Get the value of number of Character // read from the charBuffer // using read() method int value = charBuffer1.read(readonlybuff); // print the byte buffer System.out.println( "\nCharBuffer After operation is: " + Arrays.toString( charBuffer1.array()) + "\nTarget Charbuffer: " + Arrays.toString( charBuffer2.array()) + "\nno of value changed: " + value); } catch (IOException e) { System.out.println( "\nan I/O error occurs" ); System.out.println( "Exception throws: " + e); } catch (NullPointerException e) { System.out.println( "\ntarget charbuffer is null" ); System.out.println( "Exception throws: " + e); } catch (ReadOnlyBufferException e) { System.out.println( "\ntarget is a read only buffer" ); System.out.println( "Exception throws: " + e); } } } |
CharBuffer Before operation is: [x, y, z] Target Charbuffer: [a, b, c, d, e] target is a read only buffer Exception throws: java.nio.ReadOnlyBufferException
Reference: https://docs.oracle.com/javase/9/docs/api/java/nio/CharBuffer.html#read-java.nio.CharBuffer-
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