Java ByteBuffer slice()方法及示例

java.nio.ByteBuffer 类的 slice() 方法用于创建一个 新的字节缓冲区 ，其内容是给定缓冲区内容的一个共享子序列。

新缓冲区的内容将从这个缓冲区的当前位置开始。这个缓冲区的内容的变化将在新的缓冲区中可见，反之亦然。两个缓冲区的位置、极限和标记值将是独立的。

新缓冲区的位置将是0，它的容量和极限将是这个缓冲区中剩余的浮点数，而它的标记将是未定义的。新的缓冲区将是直接的，当且仅当这个缓冲区是直接的，它将是只读的，当且仅当这个缓冲区是只读的。

语法:

public abstract ByteBuffer slice()

返回值： 该方法返回 新的字节缓冲区 。

下面是说明slice()方法的例子。

例子 1 :

// Java program to demonstrate
// slice() method
 
import java.nio.*;
import java.util.*;
 
public class GFG {
 
    public static void main(String[] args)
    {
 
        // Declaring the capacity of the ByteBuffer
        int capacity = 5;
 
        // Creating the ByteBuffer
        try {
 
            // creating object of ByteBuffer
            // and allocating size capacity
            ByteBuffer bb1
                = ByteBuffer.allocate(capacity);
 
            // putting the value in ByteBuffer
            bb1.put((byte)10);
            bb1.put((byte)20);
 
            // print the ByteBuffer
            System.out.println("Original ByteBuffer: "
                               + Arrays.toString(bb1.array()));
 
            // print the ByteBuffer position
            System.out.println("\nposition:  "
                               + bb1.position());
 
            // print the ByteBuffer capacity
            System.out.println("\ncapacity:  "
                               + bb1.capacity());
 
            // Creating a shared subsequence buffer
            // of given ByteBuffer
            // using slice() method
            ByteBuffer bb2 = bb1.slice();
 
            // print the shared subsequence buffer
            System.out.println("\nshared subsequence ByteBuffer: "
                               + Arrays.toString(bb2.array()));
 
            // print the ByteBuffer position
            System.out.println("\nposition:  " + bb2.position());
 
            // print the ByteBuffer capacity
            System.out.println("\ncapacity:  " + bb2.capacity());
        }
 
        catch (IllegalArgumentException e) {
 
            System.out.println("IllegalArgumentException catched");
        }
 
        catch (ReadOnlyBufferException e) {
 
            System.out.println("ReadOnlyBufferException catched");
        }
    }
}

输出

Original ByteBuffer: [10, 20, 0, 0, 0]

position:  2

capacity:  5

shared subsequence ByteBuffer: [10, 20, 0, 0, 0]

position:  0

capacity:  3

例子 2 :

// Java program to demonstrate
// slice() method
 
import java.nio.*;
import java.util.*;
 
public class GFG {
 
    public static void main(String[] args)
    {
 
        // Declaring the capacity of the ByteBuffer
        int capacity = 5;
 
        // Creating the ByteBuffer
        try {
 
            // creating object of ByteBuffer
            // and allocating size capacity
            ByteBuffer bb1 = ByteBuffer.allocate(capacity);
 
            // putting the value in ByteBuffer
            bb1.put((byte)10)
                .put((byte)20)
                .put((byte)30)
                .put((byte)40)
                .put((byte)50);
 
            // print the ByteBuffer
            System.out.println("Original ByteBuffer: "
                               + Arrays.toString(bb1.array()));
 
            // print the ByteBuffer position
            System.out.println("\nposition:  "
                               + bb1.position());
 
            // print the ByteBuffer capacity
            System.out.println("\ncapacity:  "
                               + bb1.capacity());
 
            // Creating a shared subsequence buffer
            // of given ByteBuffer
            // using slice() method
            ByteBuffer bb2 = bb1.slice();
 
            // print the shared subsequence buffer
            System.out.println("\nshared subsequence ByteBuffer: "
                               + Arrays.toString(bb2.array()));
 
            // print the ByteBuffer position
            System.out.println("\nposition:  " + bb2.position());
 
            // print the ByteBuffer capacity
            System.out.println("\ncapacity:  " + bb2.capacity());
        }
 
        catch (IllegalArgumentException e) {
 
            System.out.println("IllegalArgumentException catched");
        }
 
        catch (ReadOnlyBufferException e) {
 
            System.out.println("ReadOnlyBufferException catched");
        }
    }
}

输出

Original ByteBuffer: [10, 20, 30, 40, 50]

position:  5

capacity:  5

shared subsequence ByteBuffer: [10, 20, 30, 40, 50]

position:  0

capacity:  0

参考资料: https://docs.oracle.com/javase/9/docs/api/java/nio/ByteBuffer.html#slice-