Java 中的 CharBuffer read()方法，示例
原文:https://www . geesforgeks . org/char buffer-read-methods-in-Java-with-examples/
java.nio.CharBuffer 类的 read() 方法用于将字符读入指定的字符缓冲区。缓冲区按原样用作字符存储库:所做的唯一更改是 put 操作的结果。不执行缓冲区的翻转或倒回。
语法:
public int read(CharBuffer target)
参数:该方法取读取字符的缓冲区。
返回值:这个方法返回添加到缓冲区的字符数，如果这个字符源在它的末尾，则返回-1。
异常:该方法抛出以下异常:-
- ioexception –If there is an I/O error
- null 指针异常你好
- readonlybufferception -If the destination is a read-only buffer
下面是举例说明 read()方法的例子:
示例 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);
}
}
}
输出:
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
示例 2: 为空指针异常
// 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);
}
}
}
T5】输出:
CharBuffer Before operation is: [x, y, z]
target charbuffer is null
Exception throws: java.lang.NullPointerException
例 3: 为 readonly buffer exception
// 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);
}
}
}
T5】输出:
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
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