极客教程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: 3
limit: 10
Compacted ShortBuffer: [0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
Position: 7
limit: 10
Updated Compacted ShortBuffer: [0, 0, 0, 0, 0, 0, 0, 961, 0, 0]
Position: 8
limit: 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: 0
limit: 10
Trying to compact the ReadOnlyBuffer sb1
Exception throws java.nio.ReadOnlyBufferException