Java FloatBuffer compact()方法及实例

java.nio.FloatBuffer 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 FloatBuffer compact()

返回值： 本方法返回新的FloatBuffer，其内容与本缓冲区的内容相同。

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 FloatBuffer
        int capacity = 10;
  
        // Creating the FloatBuffer
  
        // creating object of floatbuffer
        // and allocating size capacity
        FloatBuffer fb = FloatBuffer.allocate(capacity);
  
        // putting the value in floatbuffer
        fb.put(8.56F);
        fb.put(9.61F);
        fb.put(9.61F);
  
        // print the FloatBuffer
        System.out.println("Original FloatBuffer: "
                           + Arrays.toString(fb.array()));
  
        System.out.println("Position: " + fb.position());
  
        System.out.println("limit: " + fb.limit());
  
        // Creating a compacted  FloatBuffer of same FloatBuffer
        // using compact() method
        FloatBuffer floatBuffer = fb.compact();
  
        // print the FloatBuffer
        System.out.println("\nCompacted FloatBuffer: "
                           + Arrays.toString(floatBuffer.array()));
  
        System.out.println("Position: " + floatBuffer.position());
  
        System.out.println("limit: " + floatBuffer.limit());
  
        // putting the value in compacted floatbuffer
        floatBuffer.put(9.61F);
  
        // print the FloatBuffer
        System.out.println("\nUpdated Compacted FloatBuffer: "
                           + Arrays.toString(floatBuffer.array()));
        System.out.println("Position: " + floatBuffer.position());
        System.out.println("limit: " + floatBuffer.limit());
    }
}

输出。

Original FloatBuffer: [8.56, 9.61, 9.61, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0]
Position: 3
limit: 10

Compacted FloatBuffer: [0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0]
Position: 7
limit: 10

Updated Compacted FloatBuffer: [0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 9.61, 0.0, 0.0]
Position: 8
limit: 10

例子 2 :

// 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 FloatBuffer
        int capacity = 10;
  
        // Creating the FloatBuffer
        try {
  
            // creating object of FloatBuffer
            // and allocating size capacity
            FloatBuffer fb = FloatBuffer.allocate(capacity);
  
            // putting the value in floatbuffer
            fb.put(8.56F);
            fb.put(9.61F);
            fb.put(9.61F);
            fb.rewind();
  
            // Creating a read-only copy of FloatBuffer
            // using asReadOnlyBuffer() method
            FloatBuffer fb1 = fb.asReadOnlyBuffer();
  
            // print the ReadOnlyBuffer
            System.out.print("ReadOnlyBuffer FloatBuffer: ");
            while (fb1.hasRemaining())
                System.out.print(fb1.get() + ", ");
            System.out.println("");
  
            // print the Position of FloatBuffer fb
            System.out.println("\nPosition: " + fb.position());
  
            // print the Limit of FloatBuffer fb
            System.out.println("\nlimit: " + fb.limit());
  
            // Creating a compacted  FloatBuffer of same ReadOnlyBuffer
            // using compact() method
            System.out.println("\nTrying to compact the ReadOnlyBuffer fb1");
            FloatBuffer floatBuffer = fb1.compact();
        }
  
        catch (IllegalArgumentException e) {
  
            System.out.println("Exception throws " + e);
        }
  
        catch (ReadOnlyBufferException e) {
  
            System.out.println("Exception throws " + e);
        }
    }
}

输出。

ReadOnlyBuffer FloatBuffer: 8.56, 9.61, 9.61, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 

Position: 0

limit: 10

Trying to compact the ReadOnlyBuffer fb1
Exception throws java.nio.ReadOnlyBufferException