Java的ByteBuffer getChar() 方法和示例
获取字符()
Java.nio.ByteBuffer类的getChar()方法用于获取读取字符值的方法
在此缓冲区的当前位置读取接下来的两个字节，根据当前字节顺序将它们组合成一个 char 值，然后将位置增加 2。
句法：
public abstract char getChar()返回值：此方法返回缓冲区当前位置的字符值
抛出：此方法抛出BufferUnderflowException – 如果缓冲区的当前位置不小于其限制，则抛出此异常。
下面是说明 getChar() 方法的示例：
示例 1：
// Java program to demonstrate
// getChar() method
import java.nio.*;
import java.util.*;
public class GFG {
public static void main(String[] args)
{
// Declaring the capacity of the ByteBuffer
int capacity = 50;
// Creating the ByteBuffer
try {
// creating object of ByteBuffer
// and allocating size capacity
ByteBuffer bb = ByteBuffer.allocate(capacity);
// putting the string in the bytebuffer
bb.asCharBuffer().put("Geeks");
// rewind the Bytebuffer
bb.rewind();
// Declaring the variable
char c;
// print the ByteBuffer
System.out.println("Original ByteBuffer: ");
while ((c = bb.getChar()) != 0)
System.out.print(c + " ");
// rewind the Bytebuffer
bb.rewind();
// Reads the char at this buffer's current position
// using getChar() method
char value = bb.getChar();
// print the char value
System.out.println("\n\nByte Value: " + value);
// Reads the char at this buffer's next position
// using getChar() method
char value1 = bb.getChar();
// print the char value
System.out.print("\nNext Byte Value: " + value1);
}
catch (IllegalArgumentException e) {
System.out.println("\nException Thrown: " + e);
}
catch (ReadOnlyBufferException e) {
System.out.println("\nException Thrown: " + e);
}
catch (BufferUnderflowException e) {
System.out.println("\nException Thrown: " + e);
}
}
}
输出：
Original ByteBuffer:
G e e k s
Byte Value: G
Next Byte Value: e
示例 2：
// Java program to demonstrate
// getChar() method
import java.nio.*;
import java.util.*;
public class GFG {
public static void main(String[] args)
{
// Declaring the capacity of the ByteBuffer
int capacity = 8;
// Creating the ByteBuffer
try {
// creating object of ByteBuffer
// and allocating size capacity
ByteBuffer bb = ByteBuffer.allocate(capacity);
// putting the string in the bytebuffer
bb.asCharBuffer().put("abc");
// rewind the Bytebuffer
bb.rewind();
// Declaring the variable
char c;
// print the ByteBuffer
System.out.print("Original ByteBuffer: ");
while ((c = bb.getChar()) != 0)
System.out.print(c + " ");
// rewind the Bytebuffer
bb.rewind();
// Reads the char at this buffer's current position
// using getChar() method
char value = bb.getChar();
// print the char value
System.out.println("\n\nFirst char Value: " + value);
// Reads the char at this buffer's next position
// using getChar() method
char value1 = bb.getChar();
// print the char value
System.out.println("\nSecond char Value: " + value1);
// Reads the char at this buffer's next position
// using getChar() method
char value2 = bb.getChar();
// print the char value
System.out.println("\nThird char Value: " + value2);
// Reads the char at this buffer's next position
// using getChar() method
System.out.print("\nsince the buffer current position is incremented");
System.out.print(" to greater than its limit ");
char value3 = bb.getChar();
char value4 = bb.getChar();
}
catch (BufferOverflowException e) {
System.out.println("\nException Thrown: " + e);
}
catch (ReadOnlyBufferException e) {
System.out.println("\nException Thrown: " + e);
}
catch (BufferUnderflowException e) {
System.out.println("\nException Thrown: " + e);
}
}
}
输出：
Original ByteBuffer: a b c
First char Value: a
Second char Value: b
Third char Value: c
since the buffer current position is incremented to greater than its limit
Exception Thrown: java.nio.BufferUnderflowException
获取（整数索引）
ByteBuffer 的 get(int index) 方法用于读取给定索引处的两个字节，根据当前字节顺序将它们组合成一个 char 值。
句法：
public abstract char getChar(int index)参数：此方法将索引（将从中读取字节的索引）作为参数。
返回值：此方法返回给定索引处的字符值。
异常：此方法抛出IndexOutOfBoundsException 。如果 index 为负数或不小于缓冲区的限制，则抛出此异常。
下面是说明get(int index)方法的示例：
示例 1：
// Java program to demonstrate
// getChar() method
import java.nio.*;
import java.util.*;
public class GFG {
public static void main(String[] args)
{
// Declaring the capacity of the ByteBuffer
int capacity = 50;
// Creating the ByteBuffer
try {
// creating object of ByteBuffer
// and allocating size capacity
ByteBuffer bb = ByteBuffer.allocate(capacity);
// putting the string in the bytebuffer
bb.asCharBuffer().put("abc");
// rewind the Bytebuffer
bb.rewind();
// Declaring the variable
char c;
// print the ByteBuffer
System.out.print("Original ByteBuffer: ");
while ((c = bb.getChar()) != 0)
System.out.print(c + " ");
// rewind the Bytebuffer
bb.rewind();
// Reads the char at this buffer's at index 0
// using getChar() method
char value0 = bb.getChar(0);
// print the char value
System.out.println("\n\nchar Value at index 0: "
+ value0);
// Reads the char at this buffer's at index 2
// using getChar() method
char value1 = bb.getChar(2);
// print the char value
System.out.println("\nchar Value at index 2: "
+ value1);
// Reads the char at this buffer's at index 4
// using getChar() method
char value2 = bb.getChar(4);
// print the char value
System.out.println("\nchar Value at index 4: "
+ value2);
}
catch (IllegalArgumentException e) {
System.out.println("\nException Thrown: " + e);
}
catch (ReadOnlyBufferException e) {
System.out.println("\nException Thrown: " + e);
}
catch (BufferUnderflowException e) {
System.out.println("\nException Thrown: " + e);
}
}
}
输出：
Original ByteBuffer: a b c
char Value at index 0: a
char Value at index 2: b
char Value at index 4: c
示例 2：
// Java program to demonstrate
// getChar() method
import java.nio.*;
import java.util.*;
public class GFG {
public static void main(String[] args)
{
// Declaring the capacity of the ByteBuffer
int capacity = 50;
// Creating the ByteBuffer
try {
// creating object of ByteBuffer
// and allocating size capacity
ByteBuffer bb = ByteBuffer.allocate(capacity);
// putting the string in the bytebuffer
bb.asCharBuffer().put("abc");
// rewind the Bytebuffer
bb.rewind();
// Declaring the variable
char c;
// print the ByteBuffer
System.out.print("Original ByteBuffer: ");
while ((c = bb.getChar()) != 0)
System.out.print(c + " ");
// rewind the Bytebuffer
bb.rewind();
// Reads the char at this buffer's at index 0
// using getChar() method
char value0 = bb.getChar(0);
// print the char value
System.out.println("\n\nchar Value at index 0: "
+ value0);
// Reads the char at this buffer's at index 2
// using getChar() method
char value1 = bb.getChar(2);
// print the char value
System.out.println("\nchar Value at index 2: "
+ value1);
// Reads the char at this buffer's at index 4
// using getChar() method
System.out.println("\nTrying to get the char"
+ " at negative index ");
char value2 = bb.getChar(-4);
}
catch (IndexOutOfBoundsException e) {
System.out.println("\nException Thrown: "
+ e);
}
catch (ReadOnlyBufferException e) {
System.out.println("\nException Thrown: "
+ e);
}
catch (BufferUnderflowException e) {
System.out.println("\nException Thrown: "
+ e);
}
}
}
输出：
Original ByteBuffer: a b c
char Value at index 0: a
char Value at index 2: b
Trying to get the char at a negative index
Exception Thrown: java.lang.IndexOutOfBoundsException
参考：
- https://docs.oracle.com/javase/9/docs/api/的Java/nio/ByteBuffer.html#getChar-
- https://docs.oracle.com/javase/9/docs/api/的Java/nio/ByteBuffer.html#getChar-int-