Java IntBuffer compact()方法

java.nio.IntBuffer 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值被复制到缓冲区的开头。然后，缓冲区的位置被设置为n+1，其极限被设置为其容量。缓冲区的位置被设置为复制的浮点数。

语法

public abstract IntBuffer compact()

返回值： 该方法返回新的IntBuffer，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。

例子 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 IntBuffer
        int capacity = 10;
  
        // Creating the IntBuffer
  
        // creating object of Intbuffer
        // and allocating size capacity
        IntBuffer ib = IntBuffer.allocate(capacity);
  
        // putting the value in Intbuffer
        ib.put(8);
        ib.put(9);
        ib.put(9);
  
        // print the IntBuffer
        System.out.println("Original IntBuffer: "
                           + Arrays.toString(ib.array()));
  
        System.out.println("Position: " + ib.position());
  
        System.out.println("limit: " + ib.limit());
  
        // Creating a compacted  IntBuffer of same IntBuffer
        // using compact() method
        IntBuffer IntBuffer = ib.compact();
  
        // print the IntBuffer
        System.out.println("\nCompacted IntBuffer: "
                           + Arrays.toString(IntBuffer.array()));
  
        System.out.println("Position: " + IntBuffer.position());
  
        System.out.println("limit: " + IntBuffer.limit());
  
        // putting the value in compacted Intbuffer
        IntBuffer.put(9);
  
        // print the IntBuffer
        System.out.println("\nUpdated Compacted IntBuffer: "
                           + Arrays.toString(IntBuffer.array()));
        System.out.println("Position: " + IntBuffer.position());
        System.out.println("limit: " + IntBuffer.limit());
    }
}

输出:

Original IntBuffer: [8, 9, 9, 0, 0, 0, 0, 0, 0, 0]
Position: 3
limit: 10

Compacted IntBuffer: [0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
Position: 7
limit: 10

Updated Compacted IntBuffer: [0, 0, 0, 0, 0, 0, 0, 9, 0, 0]
Position: 8
limit: 10

实例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 IntBuffer
        int capacity = 10;
  
        // Creating the IntBuffer
        try {
  
            // creating object of IntBuffer
            // and allocating size capacity
            IntBuffer ib = IntBuffer.allocate(capacity);
  
            // putting the value in Intbuffer
            ib.put(8);
            ib.put(9);
            ib.put(9);
            ib.rewind();
  
            // Creating a read-only copy of IntBuffer
            // using asReadOnlyBuffer() method
            IntBuffer ib1 = ib.asReadOnlyBuffer();
  
            // print the ReadOnlyBuffer
            System.out.print("ReadOnlyBuffer IntBuffer: ");
  
            while (ib1.hasRemaining())
                System.out.print(ib1.get() + ", ");
            System.out.println("");
  
            // print the Position of IntBuffer ib
            System.out.println("\nPosition: " + ib.position());
  
            // print the Limit of IntBuffer ib
            System.out.println("\nlimit: " + ib.limit());
  
            // Creating a compacted  IntBuffer of same ReadOnlyBuffer
            // using compact() method
            System.out.println("\nTrying to compact the ReadOnlyBuffer ib1");
  
            IntBuffer IntBuffer = ib1.compact();
        }
  
        catch (IllegalArgumentException e) {
            System.out.println("Exception throws " + e);
        }
  
        catch (ReadOnlyBufferException e) {
            System.out.println("Exception throws " + e);
        }
    }
}

输出:

ReadOnlyBuffer IntBuffer: 8, 9, 9, 0, 0, 0, 0, 0, 0, 0, 

Position: 0

limit: 10

Trying to compact the ReadOnlyBuffer ib1
Exception throws java.nio.ReadOnlyBufferException