用示例缓冲 Java 中的 hasArray()方法
原文:https://www . geesforgeks . org/buffer-hasarray-methods-in-Java-with-examples/
java.nio.Buffer 类的 hasArray() 方法用于判断该缓冲区是否由可访问数组支持。如果此方法返回 true，则可以安全地调用数组和 arrayOffset()方法。
语法:
public abstract boolean hasArray()
返回:如果且仅当该缓冲区由数组支持且不是只读的，则该方法将返回真。否则返回假。
以下是说明 hasArray() 方法的例子:
示例 1: 当缓冲区由数组
// 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();
// Typecast bytebuffer to Buffer
Buffer buffer = (Buffer)bb;
// checking buffer is backed by array or not
boolean isArray = buffer.hasArray();
// checking if else condition
if (isArray)
System.out.println("buffer is"
+ " backed by array");
else
System.out.println("buffer is"
+ " not backed by any array");
}
catch (IllegalArgumentException e) {
System.out.println("IllegalArgumentException catched");
}
catch (ReadOnlyBufferException e) {
System.out.println("ReadOnlyBufferException catched");
}
}
}
支持时，输出:
buffer is backed by array
示例 2: 当缓冲区没有数组支持时
// 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();
// Typecast read-only ByteBuffer to read-only buffer
Buffer buffer = (Buffer)bb1;
// checking Buffer buffer is backed by array or not
boolean isArray = buffer.hasArray();
// checking if else condition
if (isArray)
System.out.println("buffer is"
+ " backed by array");
else
System.out.println("buffer is"
+ " not backed by any array");
}
catch (IllegalArgumentException e) {
System.out.println("IllegalArgumentException catched");
}
catch (ReadOnlyBufferException e) {
System.out.println("ReadOnlyBufferException catched");
}
}
}
输出:
buffer is not backed by any array
参考:https://docs . Oracle . com/javase/9/docs/API/Java/nio/buffer . html # hasArray–
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