Java ShortBuffer compact()方法及实例

java.nio.ShortBuffer 类的 compact() 方法用于压缩给定的缓冲区。缓冲区的当前位置和极限之间的短信息（如果有的话）被复制到缓冲区的开头。也就是说，索引p = position()的短文被复制到索引0，索引p + 1的短文被复制到索引1，以此类推，直到索引limit() – 1的短文被复制到索引n = limit() – 1 – p，然后缓冲区的位置被设置为n+1，其极限被设置为其容量。如果定义了标记，则被丢弃。缓冲区的位置被设置为被复制的短裤数量，而不是零，这样，在调用这个方法之后，可以立即调用另一个相对放的方法。

语法:

public abstract ShortBuffer compact()

返回值 ：该方法返回新的ShortBuffer，其内容与该缓冲区的内容相同。

异常 ：如果这个缓冲区是只读的，这个方法会抛出 ReadOnlyBufferException 。

下面的程序说明了 compact() 方法。

程序1 :

// Java program to demonstrate// compact() method  import java.nio.*;import java.util.*;  public class GFG {    public static void main(String[] args)    {          // Declaring the capacity of the ShortBuffer        int capacity = 10;          // Creating the ShortBuffer          // creating object of shortbuffer        // and allocating size capacity        ShortBuffer sb = ShortBuffer.allocate(capacity);          // putting the value in shortbuffer        sb.put((short)856);        sb.put((short)961);        sb.put((short)54);          // print the ShortBuffer        System.out.println("Original ShortBuffer: "                           + Arrays.toString(sb.array()));          System.out.println("Position: " + sb.position());          System.out.println("limit: " + sb.limit());          // Creating a compacted ShortBuffer of same ShortBuffer        // using compact() method        ShortBuffer shortBuffer = sb.compact();          // print the ShortBuffer        System.out.println("\nCompacted ShortBuffer: "                           + Arrays.toString(shortBuffer.array()));          System.out.println("Position: " + shortBuffer.position());          System.out.println("limit: " + shortBuffer.limit());          // putting the value in compacted shortbuffer        shortBuffer.put((short)961);          // print the ShortBuffer        System.out.println("\nUpdated Compacted ShortBuffer: "                           + Arrays.toString(shortBuffer.array()));        System.out.println("Position: " + shortBuffer.position());        System.out.println("limit: " + shortBuffer.limit());    }}

输出:

Original ShortBuffer: [856, 961, 54, 0, 0, 0, 0, 0, 0, 0]Position: 3limit: 10Compacted ShortBuffer: [0, 0, 0, 0, 0, 0, 0, 0, 0, 0]Position: 7limit: 10Updated Compacted ShortBuffer: [0, 0, 0, 0, 0, 0, 0, 961, 0, 0]Position: 8limit: 10

程序2： 演示ReadOnlyBufferException。

// Java program to demonstrate// compact() method  import java.nio.*;import java.util.*;  public class GFG {    public static void main(String[] args)    {          // Declaring the capacity of the ShortBuffer        int capacity = 10;          // Creating the ShortBuffer        try {              // creating object of ShortBuffer            // and allocating size capacity            ShortBuffer sb = ShortBuffer.allocate(capacity);              // putting the value in floatbuffer            sb.put((short)856);            sb.put((short)961);            sb.put((short)6010);            sb.rewind();              // Creating a read-only copy of ShortBuffer            // using asReadOnlyBuffer() method            ShortBuffer sb1 = sb.asReadOnlyBuffer();              // print the ReadOnlyBuffer            System.out.print("ReadOnlyBuffer ShortBuffer: ");            while (sb1.hasRemaining())                System.out.print(sb1.get() + ", ");            System.out.println("");              // print the Position of ShortBuffer sb            System.out.println("\nPosition: " + sb.position());              // print the Limit of ShortBuffer fb            System.out.println("\nlimit: " + sb.limit());              // Creating a compacted ShortBuffer of same ReadOnlyBuffer            // using compact() method            System.out.println("\nTrying to compact the ReadOnlyBuffer sb1");              ShortBuffer floatBuffer = sb1.compact();        }          catch (IllegalArgumentException e) {            System.out.println("Exception throws " + e);        }          catch (ReadOnlyBufferException e) {            System.out.println("Exception throws " + e);        }    }}

输出:

ReadOnlyBuffer ShortBuffer: 856, 961, 6010, 0, 0, 0, 0, 0, 0, 0, Position: 0limit: 10Trying to compact the ReadOnlyBuffer sb1Exception throws java.nio.ReadOnlyBufferException