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What is the DoubleBuffer arrayOffset() method in Java?

Kainat Asif

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 that is used to store a buffer of doubles. The arrayOffset() method of the class java.nio.DoubleBuffer is used to return the offset of the first element of the buffer inside the buffer’s backing array.

Declaration

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

buff.arrayOffset()
  • buff: The DoubleBuffer whose first element offset is required.

Return value

The DoubleBuffer.arrayOffest() method returns an int that is the offset of the first element of buff.

Note:

  • If the buffer is not backed by an accessible array, UnsupportedOperationException is thrown.
  • If the buffer is backed by an array but the array is read-only, ReadOnlyBufferException is thrown.

Examples

Example 1

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

import java.nio.*;
import java.util.*;
public class main {
public static void main(String[] args) {
int n1 = 5;
try {
DoubleBuffer buff1 = DoubleBuffer.allocate(n1);
buff1.put(1.2);
buff1.put(4.9);
System.out.println("buff1: " + Arrays.toString(buff1.array()));
int foo = buff1.arrayOffset();
System.out.println("\nbuff1 array offset: " + foo);
} catch (IllegalArgumentException e) {
System.out.println("Error!!! IllegalArgumentException");
} catch (ReadOnlyBufferException e) {
System.out.println("Error!!! ReadOnlyBufferException");
} catch (UnsupportedOperationException e) {
System.out.println("Error!!! UnsupportedOperationException");
}
}
}

Explanation

  • A DoubleBuffer buff1 is declared in line 7 with the capacity n1 = 5.
  • Two elements are added to buff1 using the put() method in lines 8-9.
  • The DoubleBuffer.arrayOffset() method is used in line 12 to get the offset of the first element of buff1 inside its backing array.

Example 2

Consider another example of the DoubleBuffer.arrayOffset() method in which ReadOnlyBufferException is thrown.

import java.nio.*;
import java.util.*;
public class main {
public static void main(String[] args) {
int n1 = 5;
try {
DoubleBuffer buff1 = DoubleBuffer.allocate(n1);
buff1.put(1.2);
buff1.put(4.9);
System.out.println("buff1: " + Arrays.toString(buff1.array()));
DoubleBuffer buff2 = buff1.asReadOnlyBuffer();
int foo = buff2.arrayOffset();
System.out.println("\nbuff2 array offset: " + foo);
} catch (IllegalArgumentException e) {
System.out.println("Error!!! IllegalArgumentException");
} catch (ReadOnlyBufferException e) {
System.out.println("Error!!! ReadOnlyBufferException");
} catch (UnsupportedOperationException e) {
System.out.println("Error!!! UnsupportedOperationException");
}
}
}

Explanation

  • A DoubleBuffer buff1 is declared in line 7 with the capacity n1 = 5.
  • Two elements are added to buff1 using the put() method in lines 8-9.
  • An DoubleBuffer buff2 is declared in line 12 that is the read-only copy of buff1.
  • The DoubleBuffer.arrayOffset() method is used in line 14 to get the offset of the first element of buff2 inside its backing array. The ReadOnlyBufferException is thrown because buff2 is read-only.

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Kainat Asif
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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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