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What is the doubleBuffer clear() method in Java?

Syed Muhammad Ali Mustafa

Grokking Modern System Design Interview for Engineers & Managers

Ace your System Design Interview and take your career to the next level. Learn to handle the design of applications like Netflix, Quora, Facebook, Uber, and many more in a 45-min interview. Learn the RESHADED framework for architecting web-scale applications by determining requirements, constraints, and assumptions before diving into a step-by-step design process.

java.nio.DoubleBuffer is a class we can use to store a buffer of doubles. We can use this class’s clear() method to clear a buffer. Clearing a buffer means:

  • We set the buffer position to 0.
  • We set the buffer limit to the buffer capacity. Capacity is the number of elements a buffer contains. The limit of a buffer is its first index that should not be read or written. The limit of a buffer should be less than or equal to its capacity.
  • We discard the mark. Marking a position means recording a position that can be restored by the DoubleBuffer.reset() method. This marked position is discarded by the DoubleBuffer.clear() method.

Declaration

The DoubleBuffer.clear() method is declared as follows:

buff.clear()
  • buff: The DoubleBuffer to be cleared.

Return value

The DoubleBuffer.clear() method returns the DoubleBuffer buff after cleaning it.

Code

Consider the code snippet below, which demonstrates the use of the DoubleBuffer.clear() method.

import java.nio.*;
import java.util.*;
public class main {
public static void main(String[] args) {
int n1 = 4;
DoubleBuffer buff1 = DoubleBuffer.allocate(n1);
buff1.put(1.7);
buff1.put(4.9);
buff1.limit(3);
buff1.mark();
System.out.println("buff1: " + Arrays.toString(buff1.array()));
System.out.println("position at(before clear): " + buff1.position());
System.out.println("Limit at(before clear): " + buff1.limit());
buff1.mark();
System.out.println("clear()");
buff1.clear();
System.out.println("position at(after rewind): " + buff1.position());
System.out.println("Limit at(before clear): " + buff1.limit());
}
}

Explanation

  • A DoubleBuffer buff1 is declared in line 7 with the capacity n1 = 4.
  • Two elements are added to buff1 using the put() method in lines 8-9. After adding the first element, the position of buff1 is incremented from 0 to 1. After adding the second element, the position of buff1 is incremented from 1 to 2.
  • The position of buff1 before clear() is 2. After calling the clear() method in line 21, the position of buff1 is set to 0.
  • The limit of buff1 is set to 3 using the limit() method in line 11. The limit of buff1 before clear is 3. After calling the clear() method in line 21, the limit of buff1 is set to its capacity, which is 4.
  • The position of buff1 is marked to 2 using the mark() method in line 12. After calling the clear() method in line 21, the mark of buff1 is discarded and the position is set to 0.

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Syed Muhammad Ali Mustafa
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Grokking Modern System Design Interview for Engineers & Managers

Ace your System Design Interview and take your career to the next level. Learn to handle the design of applications like Netflix, Quora, Facebook, Uber, and many more in a 45-min interview. Learn the RESHADED framework for architecting web-scale applications by determining requirements, constraints, and assumptions before diving into a step-by-step design process.

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