Java ByteBuffer wrap()用法及代碼示例

wrap(byte[] array)

java.nio.ByteBuffer類的wrap()方法用於將字節數組包裝到緩衝區中。新緩衝區將由給定的字節數組支持；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 ByteBuffer wrap(float[] array)

參數：此方法將float數組作為參數，它將是支持此緩衝區的數組。

返回值：此方法返回新的字節緩衝區。

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 byte array 
        byte[] bbb = { 10, 20, 30 }; 
  
        // print the byte array length 
        System.out.println("Array length : "
                           + bbb.length); 
  
        // print the byte array element 
        System.out.println("\nArray element : "
                           + Arrays.toString(bbb)); 
  
        // wrap the byte array into byteBuffer 
        // using wrap() method 
        ByteBuffer byteBuffer = ByteBuffer.wrap(bbb); 
  
        // Rewind the ByteBuffer 
        byteBuffer.rewind(); 
  
        // print the byte buffer 
        System.out.println("\nbyteBuffer : "
                           + Arrays.toString(byteBuffer.array())); 
  
        // print the ByteBuffer capacity 
        System.out.println("\nbyteBuffer capacity : "
                           + byteBuffer.capacity()); 
  
        // print the ByteBuffer position 
        System.out.println("\nbyteBuffer position:  "
                           + byteBuffer.position()); 
    } 
}

輸出：

Array length : 3

Array element : [10, 20, 30]

byteBuffer : [10, 20, 30]

byteBuffer capacity : 3

byteBuffer position:  0

參考： https://docs.oracle.com/javase/9/docs/api/java/nio/ByteBuffer.html#wrap-byte:A-

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

新緩衝區將由給定的字節數組支持；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 ByteBuffer wrap(byte[] 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：此方法返回新的字節緩衝區。

拋出：此方法拋出IndexOutOfBoundsException(如果offset和length參數的前提條件不成立)。

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 byte array 
        byte[] bbb = { 10, 20, 30 }; 
  
        // print the byte array length 
        System.out.println("Array length : "
                           + bbb.length); 
  
        // print the byte array element 
        System.out.println("\nArray element : "
                           + Arrays.toString(bbb)); 
  
        // wrap the byte array into ByteBuffer 
        // using wrap() method 
        ByteBuffer byteBuffer = ByteBuffer.wrap(bbb, 0, 
                                                bbb.length); 
  
        // Rewind the bytebuffer 
        byteBuffer.rewind(); 
  
        // print the byte buffer 
        System.out.println("\nbyteBuffer : "
                           + Arrays.toString(byteBuffer.array())); 
  
        // print the ByteBuffer capacity 
        System.out.println("\nbyteBuffer capacity : "
                           + byteBuffer.capacity()); 
  
        // print the ByteBuffer position 
        System.out.println("\nbyteBuffer position:  "
                           + byteBuffer.position()); 
    } 
}

輸出：

Array length : 3

Array element : [10, 20, 30]

byteBuffer : [10, 20, 30]

byteBuffer capacity : 3

byteBuffer position:  0

範例2：演示NullPointerException

// 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 byte array 
        byte[] bbb = { 10, 20, 30 }; 
  
        // print the byte array length 
        System.out.println("Array length : " + bbb.length); 
  
        // print the byte array element 
        System.out.println("\nArray element : " + Arrays.toString(bbb)); 
  
        try { 
            // wrap the byte array into byteBuffer 
            // using wrap() method 
            System.out.println("\nHere "
                               + "offset and length does not hold"
                               + " the required condition "); 
            ByteBuffer byteBuffer = ByteBuffer.wrap(bbb, 
                                                    1, 
                                                    bbb.length); 
  
            // Rewind the bytebuffer 
            byteBuffer.rewind(); 
  
            // print the byte buffer 
            System.out.println("\nbyteBuffer : "
                               + Arrays.toString(byteBuffer.array())); 
  
            // print the byteBuffer capacity 
            System.out.println("\nbytebuffer capacity : "
                               + byteBuffer.capacity()); 
  
            // print the byteBuffer position 
            System.out.println("\nbytebuffer position:  "
                               + byteBuffer.position()); 
        } 
        catch (IndexOutOfBoundsException e) { 
            System.out.println("Exception throws:  " + e); 
        } 
    } 
}

輸出：

Array length : 3

Array element : [10, 20, 30]

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

參考： https://docs.oracle.com/javase/9/docs/api/java/nio/ByteBuffer.html#wrap-byte:A-int-int-

相關用法

注：本文由純淨天空篩選整理自RohitPrasad3大神的英文原創作品 ByteBuffer 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。