Java 中的 DoubleBuffer hasArray()方法，示例
原文:https://www . geesforgeks . org/double buffer-hasarray-method-in-Java-with-examples/
java.nio.DoubleBuffer 类的 hasArray() 方法用于确保给定的缓冲区是否由可访问的浮点数组支持。如果该缓冲区有可访问的后备数组，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，因为它们在支持数组上工作。
语法:
public final 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。否则它返回假。
下面是一些示例来说明 hasArray()方法:
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 DoubleBuffer
int capacity = 10;
// Creating the DoubleBuffer
try {
// creating object of Doublebuffer
// and allocating size capacity
DoubleBuffer fb = DoubleBuffer.allocate(capacity);
// putting the value in Doublebuffer
fb.put(8.56F);
fb.put(2, 9.61F);
fb.rewind();
// checking DoubleBuffer fb is backed by array or not
boolean isArray = fb.hasArray();
// checking if else condition
if (isArray)
System.out.println("DoubleBuffer fb is"
+ " backed by array");
else
System.out.println("DoubleBuffer fb is"
+ " not backed by any array");
}
catch (IllegalArgumentException e) {
System.out.println("IllegalArgumentException catched");
}
catch (ReadOnlyBufferException e) {
System.out.println("ReadOnlyBufferException catched");
}
}
}
Output:
DoubleBuffer fb 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 DoubleBuffer
int capacity = 10;
// Creating the DoubleBuffer
try {
// creating object of Doublebuffer
// and allocating size capacity
DoubleBuffer fb = DoubleBuffer.allocate(capacity);
// putting the value in Doublebuffer
fb.put(8.56F);
fb.put(2, 9.61F);
fb.rewind();
// Creating a read-only copy of DoubleBuffer
// using asReadOnlyBuffer() method
DoubleBuffer fb1 = fb.asReadOnlyBuffer();
// checking DoubleBuffer fb is backed by array or not
boolean isArray = fb1.hasArray();
// checking if else condition
if (isArray)
System.out.println("DoubleBuffer fb is"
+ " backed by array");
else
System.out.println("DoubleBuffer fb is"
+ " not backed by any array");
}
catch (IllegalArgumentException e) {
System.out.println("IllegalArgumentException catched");
}
catch (ReadOnlyBufferException e) {
System.out.println("ReadOnlyBufferException catched");
}
}
}
Output:
DoubleBuffer fb is not backed by any array
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