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Java DoubleBuffer wrap()用法及代码示例


wrap(double[] array)

java.nio.DoubleBuffer类的wrap()方法用于将双精度数组包装到缓冲区中。新缓冲区将由给定的double数组支持；也就是说，对缓冲区的修改将导致数组被修改，反之亦然。新缓冲区的容量和限制为array.length，位置为零，标记未定义。它的支持数组将是给定的数组，其数组偏移量将为零。

用法:

public static DoubleBuffer wrap(double[] array)

参数：此方法将数组(将支持此缓冲区的数组)作为参数。


返回值：此方法返回新的双缓冲区。

下面是说明wrap()方法的示例：

// Java program to demonstrate 
// wrap() method 
  
import java.nio.*; 
import java.util.*; 
  
public class GFG { 
    public static void main(String[] args) 
    { 
  
        // Declaire and initialize the float array 
        double[] fbb = { 1.23D, 2.34D, 4.56D }; 
  
        // print the float array length 
        System.out.println("Array length : " + fbb.length); 
  
        // print the float array element 
        System.out.println("\nArray element : "
                           + Arrays.toString(fbb)); 
  
        // wrap the float array into floatBuffer 
        // using wrap() method 
        DoubleBuffer doubleBuffer = DoubleBuffer.wrap(fbb); 
  
        // Rewind the floatbuffer 
        doubleBuffer.rewind(); 
  
        // print the float buffer 
        System.out.println("\ndoubleBuffer : "
                           + Arrays.toString(doubleBuffer.array())); 
  
        // print the DoubleBuffer capacity 
        System.out.println("\ndoublebuffer capacity : "
                           + doubleBuffer.capacity()); 
  
        // print the DoubleBuffer position 
        System.out.println("\ndoublebuffer position:  "
                           + doubleBuffer.position()); 
    } 
}
输出： 
Array length : 3

Array element : [1.23, 2.34, 4.56]

doubleBuffer : [1.23, 2.34, 4.56]

doublebuffer capacity : 3

doublebuffer position:  0

wrap(double[] array, int offset, int length)

新缓冲区将由给定的double数组支持；也就是说，对缓冲区的修改将导致数组被修改，反之亦然。新缓冲区的容量将为array.length，其位置将偏移，其限制将为offset + length，其标记将是不确定的。它的支持数组将是给定的数组，其数组偏移量将为零。

用法:

public static FloatBuffer wrap (double[] array, int offset, int length)

参数：此方法采用以下参数：

  • array:将支持新缓冲区的数组。
  • offset:要使用的子数组的偏移量；必须为非负数，且不得大于array.length。新缓冲区的位置将设置为此值。
  • length:要使用的子数组的长度；必须为非负且不大于array.length –偏移量。新缓冲区的限制将设置为偏移量+长度。

返回值：此方法返回新的双缓冲区。

异常：如果offset和length参数的前提条件不成立，则此方法将引发IndexOutOfBoundsException。

下面是说明wrap()方法的示例：

范例1：

// Java program to demonstrate 
// wrap() method 
  
import java.nio.*; 
import java.util.*; 
  
public class GFG { 
  
    public static void main(String[] args) 
    { 
  
        // Declare and initialize the float array 
        double[] fbb = { 1.23D, 2.34D, 4.56D }; 
  
        // print the float array length 
        System.out.println("Array length : " + fbb.length); 
  
        // print the float array element 
        System.out.println("\nArray element : "
                           + Arrays.toString(fbb)); 
  
        // wrap the double array into floatBuffer 
        // using wrap() method 
        DoubleBuffer doubleBuffer = DoubleBuffer.wrap(fbb, 0, 
                                                      fbb.length); 
  
        // Rewind the doublebuffer 
        doubleBuffer.rewind(); 
  
        // print the float buffer 
        System.out.println("\ndoubleBuffer : "
                           + Arrays.toString(doubleBuffer.array())); 
  
        // print the FloatBuffer capacity 
        System.out.println("\ndoublebuffer capacity : "
                           + doubleBuffer.capacity()); 
  
        // print the FloatBuffer position 
        System.out.println("\ndoublebuffer position:  "
                           + doubleBuffer.position()); 
    } 
}
输出： 
Array length : 3

Array element : [1.23, 2.34, 4.56]

doubleBuffer : [1.23, 2.34, 4.56]

doublebuffer capacity : 3

doublebuffer position:  0

范例2：演示IndexOutOfBoundsException

// Java program to demonstrate 
// asReadOnlyBuffer() method 
  
import java.nio.*; 
import java.util.*; 
  
public class GFG { 
  
    public static void main(String[] args) 
    { 
  
        // Declare and initialize the Double array 
        double[] fbb = { 1.23D, 2.34D, 4.56D }; 
  
        // print the Double array length 
        System.out.println("Array length : " + fbb.length); 
  
        // print the Double array element 
        System.out.println("\nArray element : " + Arrays.toString(fbb)); 
  
        try { 
            // wrap the Double array into floatBuffer 
            // using wrap() method 
            System.out.println("\nHere "
                               + "offset and length does not hold"
                               + " the required condition "); 
            DoubleBuffer doubleBuffer = DoubleBuffer.wrap(fbb, 
                                                          1, 
                                                          fbb.length); 
  
            // Rewind the Doublebuffer 
            doubleBuffer.rewind(); 
  
            // print the Double buffer 
            System.out.println("\ndoubleBuffer : "
                               + Arrays.toString(doubleBuffer.array())); 
  
            // print the DoubleBuffer capacity 
            System.out.println("\ndoublebuffer capacity : "
                               + doubleBuffer.capacity()); 
  
            // print the DoubleBuffer position 
            System.out.println("\ndoublebuffer position:  "
                               + doubleBuffer.position()); 
        } 
        catch (IndexOutOfBoundsException e) { 
            System.out.println("Exception throws:  " + e); 
        } 
    } 
}
输出： 
Array length : 3

Array element : [1.23, 2.34, 4.56]

Here offset and length does not hold the required condition 
Exception throws:  java.lang.IndexOutOfBoundsException


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注：本文由纯净天空筛选整理自pawan_asipu大神的英文原创作品 DoubleBuffer wrap() method in Java with Examples。非经特殊声明，原始代码版权归原作者所有，本译文未经允许或授权，请勿转载或复制。