Java Buffer limit()方法及示例

java.nio.Buffer类的 limit() 方法是用来设置这个缓冲区的极限。如果位置大于新的极限，那么它将被设置为新的极限。如果标记被定义并且大于新的极限，那么它将被丢弃。

语法

public Buffer limit(int newLimit)

返回值： 该方法返回这个缓冲区。

下面是说明limit()方法的例子。

例子 1 :

// Java program to demonstrate
// limit() method
  
import java.nio.*;
import java.util.*;
  
public class GFG {
    public static void main(String[] args)
    {
        // defining and allocating ByteBuffer
        // using allocate() method
        ByteBuffer byteBuffer
            = ByteBuffer.allocate(4);
  
        // put byte value in byteBuffer
        // using put() method
        byteBuffer.put((byte)20);
        byteBuffer.put((byte)30);
  
        // Typecast byteBuffer to buffer
        Buffer buffer = (Buffer)byteBuffer;
  
        // print the byte buffer
        System.out.println("Buffer before operation: "
                           + Arrays.toString(
                                 (byte[])buffer.array())
                           + "\nPosition: "
                           + buffer.position()
                           + "\nLimit: "
                           + buffer.limit());
  
        // Limit the Buffer
        // using limit() method
        buffer.limit(1);
  
        // print the buffer
        System.out.println("\nBuffer after operation: "
                           + Arrays.toString(
                                 (byte[])buffer.array())
                           + "\nPosition: "
                           + buffer.position()
                           + "\nLimit: "
                           + buffer.limit());
    }
}

输出:

Buffer before operation: [20, 30, 0, 0]
Position: 2
Limit: 4

Buffer after operation: [20, 30, 0, 0]
Position: 1
Limit: 1

例子 2 :

// Java program to demonstrate
// limit() method
  
import java.nio.*;
import java.util.*;
  
public class GFG {
    public static void main(String[] args)
    {
        // defining and allocating ByteBuffer
        // using allocate() method
        ByteBuffer byteBuffer
            = ByteBuffer.allocate(5);
  
        // put byte value in byteBuffer
        // using put() method
        byteBuffer.put((byte)20);
        byteBuffer.put((byte)30);
        byteBuffer.put((byte)40);
  
        // Typecast byteBuffer to buffer
        Buffer buffer = (Buffer)byteBuffer;
  
        // mark will be going to discarded by limit()
        buffer.mark();
  
        // print the buffer
        System.out.println("Buffer before operation: "
                           + Arrays.toString(
                                 (byte[])buffer.array())
                           + "\nPosition: "
                           + buffer.position()
                           + "\nLimit: "
                           + buffer.limit());
  
        // Limit the Buffer
        // using limit() method
        buffer.limit(4);
  
        // print the buffer
        System.out.println("\nBuffer after operation: "
                           + Arrays.toString(
                                 (byte[])buffer.array())
                           + "\nPosition: "
                           + buffer.position()
                           + "\nLimit: "
                           + buffer.limit());
    }
}

输出:

Buffer before operation: [20, 30, 40, 0, 0]
Position: 3
Limit: 5

Buffer after operation: [20, 30, 40, 0, 0]
Position: 3
Limit: 4

参考资料: https://docs.oracle.com/javase/9/docs/api/java/nio/Buffer.html#limit-int-