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Java DoubleBuffer wrap()用法及代碼示例


wrap(double[] array)

java.nio.DoubleBuffer類的wrap()方法用於將雙精度數組包裝到緩衝區中。新緩衝區將由給定的double數組支持；也就是說，對緩衝區的修改將導致數組被修改，反之亦然。新緩衝區的容量和限製為array.length，位置為零，標記未定義。它的支持數組將是給定的數組，其數組偏移量將為零。

用法:

public static DoubleBuffer wrap(double[] array)

參數：此方法將數組(將支持此緩衝區的數組)作為參數。


返回值：此方法返回新的雙緩衝區。

下麵是說明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()); 
    } 
}
輸出： 
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)

新緩衝區將由給定的double數組支持；也就是說，對緩衝區的修改將導致數組被修改，反之亦然。新緩衝區的容量將為array.length，其位置將偏移，其限製將為offset + length，其標記將是不確定的。它的支持數組將是給定的數組，其數組偏移量將為零。

用法:

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

參數：此方法采用以下參數：

  • array:將支持新緩衝區的數組。
  • offset:要使用的子數組的偏移量；必須為非負數，且不得大於array.length。新緩衝區的位置將設置為此值。
  • length:要使用的子數組的長度；必須為非負且不大於array.length –偏移量。新緩衝區的限製將設置為偏移量+長度。

返回值：此方法返回新的雙緩衝區。

異常：如果offset和length參數的前提條件不成立，則此方法將引發IndexOutOfBoundsException。

下麵是說明wrap()方法的示例：

範例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()); 
    } 
}
輸出： 
Array length : 3

Array element : [1.23, 2.34, 4.56]

doubleBuffer : [1.23, 2.34, 4.56]

doublebuffer capacity : 3

doublebuffer position:  0

範例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); 
        } 
    } 
}
輸出： 
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：本文由純淨天空篩選整理自pawan_asipu大神的英文原創作品 DoubleBuffer wrap() method in Java with Examples。非經特殊聲明，原始代碼版權歸原作者所有，本譯文未經允許或授權，請勿轉載或複製。