Java中的 LongBuffer limit() 方法及示例

Java.nio.LongBuffer 类的limit()方法用来修改这个LongBuffer 的限制。此方法将要设置的限制作为参数，并将其设置为此 Buffer 的新限制。如果这个 Buffer 的标记已经定义并且大于新的指定限制，那么这个新的限制不会被设置并被丢弃。

句法：

public final LongBuffer limit(int newLimit)

参数：该方法接受一个整数类型的参数newLimit ，它指的是要设置为缓冲区的新限制的限制。

返回值：该方法将指定的新限制设置为该Buffer的新限制后返回该缓冲区。

以下是说明 limit() 方法的示例：

示例 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 LongBuffer
        // using allocate() method
        LongBuffer longBuffer
            = LongBuffer.allocate(4);
  
        // put long value in longBuffer
        // using put() method
        longBuffer.put(20);
        longBuffer.put(30);
  
        // print the long buffer
        System.out.println(
            "LongBuffer before "
            + "setting buffer's limit: "
            + Arrays.toString(
                  longBuffer.array())
            + "\nPosition: "
            + longBuffer.position()
            + "\nLimit: "
            + longBuffer.limit());
  
        // Limit the longBuffer
        // using limit() method
        longBuffer.limit(1);
  
        // print the long buffer
        System.out.println(
            "\nLongBuffer after "
            + "setting buffer's limit: "
            + Arrays.toString(
                  longBuffer.array())
            + "\nPosition: "
            + longBuffer.position()
            + "\nLimit: "
            + longBuffer.limit());
    }
}

输出：

LongBuffer before setting buffer's limit: [20, 30, 0, 0]
Position: 2
Limit: 4

LongBuffer after setting buffer's limit: [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 LongBuffer
        // using allocate() method
        LongBuffer longBuffer
            = LongBuffer.allocate(5);
  
        // put double value in LongBuffer
        // using put() method
        longBuffer.put(20);
        longBuffer.put(30);
        longBuffer.put(40);
  
        // mark will be going to
        // discarded by limit()
        longBuffer.mark();
  
        // print the long buffer
        System.out.println(
            "LongBuffer before "
            + "setting buffer's limit: "
            + Arrays.toString(
                  longBuffer.array())
            + "\nPosition: "
            + longBuffer.position()
            + "\nLimit: "
            + longBuffer.limit());
  
        // Limit the longBuffer
        // using limit() method
        longBuffer.limit(4);
  
        // print the long buffer
        System.out.println(
            "\nLongBuffer before "
            + "setting buffer's limit: "
            + Arrays.toString(
                  longBuffer.array())
            + "\nPosition: "
            + longBuffer.position()
            + "\nLimit: "
            + longBuffer.limit());
    }
}

输出：

LongBuffer before setting buffer's limit: [20, 30, 40, 0, 0]
Position: 3
Limit: 5

LongBuffer before setting buffer's limit: [20, 30, 40, 0, 0]
Position: 3
Limit: 4

参考： https://docs.oracle.com/javase/9/docs/api/ Java/nio/LongBuffer.html#rewind–