Java中的 ByteBuffer hasArray() 方法及示例
Java.nio.ByteBuffer类的hasArray()方法用于确保给定缓冲区是否由可访问的字节数组支持。如果此缓冲区有可访问的支持数组,则返回 true,否则返回 false。如果此方法返回 true,则可以安全地调用 array() 和 arrayOffset() 方法,因为它们在后备数组上工作。
句法:
public final boolean hasArray()
返回:当且仅当此缓冲区由数组支持并且不是只读的时,此方法才会返回true 。否则返回false 。
下面是说明hasArray()方法的示例:
示例 1:当缓冲区由数组支持时
// Java program to demonstrate
// hasArray() method
import java.nio.*;
import java.util.*;
public class GFG {
public static void main(String[] args)
{
// Declaring the capacity of the ByteBuffer
int capacity = 10;
// Creating the ByteBuffer
try {
// creating object of bytebuffer
// and allocating size capacity
ByteBuffer bb = ByteBuffer.allocate(capacity);
// putting the value in bytebuffer
bb.put((byte)10);
bb.put((byte)20);
bb.rewind();
// checking FloatBuffer fb is backed by array or not
boolean isArray = bb.hasArray();
// checking if else condition
if (isArray)
System.out.println("ByteBuffer bb is"
+ " backed by array");
else
System.out.println("ByteBuffer bb is"
+ " not backed by any array");
}
catch (IllegalArgumentException e) {
System.out.println("IllegalArgumentException catched");
}
catch (ReadOnlyBufferException e) {
System.out.println("ReadOnlyBufferException catched");
}
}
}
输出:
ByteBuffer bb is backed by array
示例 2:当缓冲区由数组支持时
// Java program to demonstrate
// hasArray() method
import java.nio.*;
import java.util.*;
public class GFG {
public static void main(String[] args)
{
// Declaring the capacity of the ByteBuffer
int capacity = 10;
// Creating the ByteBuffer
try {
// creating object of ByteBuffer
// and allocating size capacity
ByteBuffer bb = ByteBuffer.allocate(capacity);
// putting the value in ByteBuffer
bb.put((byte)8.56F);
bb.put((byte)10);
bb.rewind();
// Creating a read-only copy of ByteBuffer
// using asReadOnlyBuffer() method
ByteBuffer bb1 = bb.asReadOnlyBuffer();
// checking ByteBuffer bb is backed by array or not
boolean isArray = bb1.hasArray();
// checking if else condition
if (isArray)
System.out.println("ByteBuffer bb is"
+ " backed by array");
else
System.out.println("ByteBuffer bb is"
+ " not backed by any array");
}
catch (IllegalArgumentException e) {
System.out.println("IllegalArgumentException catched");
}
catch (ReadOnlyBufferException e) {
System.out.println("ReadOnlyBufferException catched");
}
}
}
输出:
ByteBuffer bb is not backed by any array
参考: https://docs.oracle.com/javase/9/docs/api/ Java/nio/ByteBuffer.html#hasArray–