Java CharBuffer arrayOffset()方法
java.nio.CharBuffer 类的 arrayOffset() 方法是用来返回缓冲区的第一个元素在缓冲区的支持数组中的偏移。这意味着如果这个缓冲区是由一个数组支持的,那么缓冲区的位置p对应于数组索引p + arrayOffset()。
为了检查这个缓冲区是否有一个支持的数组,可以使用 hasArray() 方法。它可以确保这个缓冲区有一个可访问的支持数组。
语法
public final int arrayOffset()
返回值: 该方法返回该缓冲区的第一个元素在该缓冲区的数组中的偏移。
异常: 如果这个缓冲区是由一个数组支持的,但是是只读的,这个方法会抛出 ReadOnlyBufferException 。
下面的程序说明了 arrayOffset() 方法。
例1 :
// Java program to demonstrate
// arrayOffset() method
import java.nio.*;
import java.util.*;
public class GFG {
public static void main(String[] args)
{
// Declaring the capacity of the CharBuffer
int capacity = 10;
// Creating the CharBuffer
try {
// creating object of CharBuffer
// and allocating size capacity
CharBuffer cb = CharBuffer.allocate(capacity);
// putting the value in CharBuffer
cb.put('a');
cb.put(2, 'b');
// print the CharBuffer
System.out.println("CharBuffer: "
+ Arrays.toString(cb.array()));
// print the arrayOffset
System.out.println("arrayOffset: "
+ cb.arrayOffset());
}
catch (IllegalArgumentException e) {
System.out.println("IllegalArgumentException catched");
}
catch (ReadOnlyBufferException e) {
System.out.println("Exception throws" + e);
}
}
}
输出:
CharBuffer: [a, , b, , , , , , , ]
arrayOffset: 0
例2: 演示ReadOnlyBufferException
// Java program to demonstrate
// arrayOffset() method
import java.nio.*;
import java.util.*;
public class GFG {
public static void main(String[] args)
{
// Declaring the capacity of the CharBuffer
int capacity = 10;
// Creating the CharBuffer
try {
// creating object of CharBuffer
// and allocating size capacity
CharBuffer fb = CharBuffer.allocate(capacity);
// putting the value in CharBuffer
fb.put('a');
fb.put(2, 'b');
fb.rewind();
// Creating a read-only copy of CharBuffer
// using asReadOnlyBuffer() method
CharBuffer cb1 = fb.asReadOnlyBuffer();
// print the CharBuffer
System.out.print("Read only buffer : ");
while (cb1.hasRemaining())
System.out.print(cb1.get() + ", ");
// next line
System.out.println("");
// print the arrayOffset
System.out.println("\nTry to print the array offset"
+ " of read only buffer");
System.out.println("arrayOffset: " + cb1.arrayOffset());
}
catch (IllegalArgumentException e) {
System.out.println("Exception throws: " + e);
}
catch (ReadOnlyBufferException e) {
System.out.println("Exception throws: " + e);
}
}
}
输出:
Read only buffer : a, , b, , , , , , , ,
Try to print the array offset of read only buffer
Exception throws: java.nio.ReadOnlyBufferException