Java DoubleBuffer limit()方法及实例

java.nio.DoubleBuffer类的 limit() 方法是用来修改这个DoubleBuffer的极限。这个方法以要设置的极限为参数，并将其设置为这个Buffer的新极限。如果这个Buffer的标记已经被定义，并且大于新指定的极限，那么这个新的极限就不会被设置并被丢弃。

语法

public final DoubleBuffer limit(int newLimit)

返回值： 该方法在将指定的新极限作为该Buffer的新极限后返回该Buffer。

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 DoubleBuffer
        // using allocate() method
        DoubleBuffer doubleBuffer
            = DoubleBuffer.allocate(4);
  
        // put double value in doubleBuffer
        // using put() method
        doubleBuffer.put(20.5);
        doubleBuffer.put(30.5);
  
        // print the double buffer
        System.out.println("DoubleBuffer before "
                           + "setting buffer's limit: "
                           + Arrays.toString(
                                 doubleBuffer.array())
                           + "\nPosition: "
                           + doubleBuffer.position()
                           + "\nLimit: "
                           + doubleBuffer.limit());
  
        // Limit the doubleBuffer
        // using limit() method
        doubleBuffer.limit(1);
  
        // print the double buffer
        System.out.println("\nDoubleBuffer after "
                           + "setting buffer's limit: "
                           + Arrays.toString(
                                 doubleBuffer.array())
                           + "\nPosition: "
                           + doubleBuffer.position()
                           + "\nLimit: "
                           + doubleBuffer.limit());
    }
}

输出:

DoubleBuffer before setting buffer's limit: [20.5, 30.5, 0.0, 0.0]
Position: 2
Limit: 4

DoubleBuffer after setting buffer's limit: [20.5, 30.5, 0.0, 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 DoubleBuffer
        // using allocate() method
        DoubleBuffer doubleBuffer
            = DoubleBuffer.allocate(5);
  
        // put double value in DoubleBuffer
        // using put() method
        doubleBuffer.put(20.5);
        doubleBuffer.put(30.5);
        doubleBuffer.put(40.5);
  
        // mark will be going to
        // discarded by limit()
        doubleBuffer.mark();
  
        // print the double buffer
        System.out.println("DoubleBuffer before "
                           + "setting buffer's limit: "
                           + Arrays.toString(
                                 doubleBuffer.array())
                           + "\nPosition: "
                           + doubleBuffer.position()
                           + "\nLimit: "
                           + doubleBuffer.limit());
  
        // Limit the doubleBuffer
        // using limit() method
        doubleBuffer.limit(4);
  
        // print the double buffer
        System.out.println("\nDoubleBuffer before "
                           + "setting buffer's limit: "
                           + Arrays.toString(
                                 doubleBuffer.array())
                           + "\nPosition: "
                           + doubleBuffer.position()
                           + "\nLimit: "
                           + doubleBuffer.limit());
    }
}

输出:

DoubleBuffer before setting buffer's limit: [20.5, 30.5, 40.5, 0.0, 0.0]
Position: 3
Limit: 5

DoubleBuffer before setting buffer's limit: [20.5, 30.5, 40.5, 0.0, 0.0]
Position: 3
Limit: 4

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