Java中的 ByteBuffer limit() 方法及示例

Java.nio.ByteBuffer 类的limit()方法用于设置这个缓冲区的限制。如果头寸大于新限制，则将其设置为新限制。如果标记已定义且大于新限制，则将其丢弃。

句法：

public ByteBuffer limit(int newLimit)

返回值：此方法返回此缓冲区。

以下是说明 limit() 方法的示例：

示例 1：

// Java program to demonstrate
// compact() 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);
  
        // print the byte buffer
        System.out.println("ByteBuffer before compact: "
                           + Arrays.toString(byteBuffer.array())
                           + "\nPosition: " + byteBuffer.position()
                           + "\nLimit: " + byteBuffer.limit());
  
        // Limit the byteBuffer
        // using limit() method
        byteBuffer.limit(1);
  
        // print the byte buffer
        System.out.println("\nByteBuffer after compact: "
                           + Arrays.toString(byteBuffer.array())
                           + "\nPosition: " + byteBuffer.position()
                           + "\nLimit: " + byteBuffer.limit());
    }
}

输出：

ByteBuffer before compact: [20, 30, 0, 0]
Position: 2
Limit: 4

ByteBuffer after compact: [20, 30, 0, 0]
Position: 1
Limit: 1

示例 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);
  
        // mark will be going to discarded by limit()
        byteBuffer.mark();
  
        // print the byte buffer
        System.out.println("ByteBuffer before compact: "
                           + Arrays.toString(byteBuffer.array())
                           + "\nPosition: " + byteBuffer.position()
                           + "\nLimit: " + byteBuffer.limit());
  
        // Limit the byteBuffer
        // using limit() method
        byteBuffer.limit(4);
  
        // print the byte buffer
        System.out.println("\nByteBuffer after compact: "
                           + Arrays.toString(byteBuffer.array())
                           + "\nPosition: " + byteBuffer.position()
                           + "\nLimit: " + byteBuffer.limit());
    }
}

输出：

ByteBuffer before compact: [20, 30, 40, 0, 0]
Position: 3
Limit: 5

ByteBuffer after compact: [20, 30, 40, 0, 0]
Position: 3
Limit: 4

参考： https://docs.oracle.com/javase/9/docs/api/ Java/nio/ByteBuffer.html#limit-int-