CODEWITHSUNDEEP
javaarraysclass
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Reputation: 112

Where is size getting it's value (Java)

Where is "int size " getting it's value from? I read code like 1000 times,but I still have no clue where is "size" initialized, I am new in java, but I don't understand this one,code is working fine any help would be nice. thanks in advance

public class Study {
  public static void main(String[] args) {
    Queue queue = new Queue();
    for (int i = 0; i <= 20; i++)
      queue.enqueue(i);

    while (!queue.empty())
      System.out.print(queue.dequeue() + " ");
  }
}

class Queue {
  private int[] elements;
  private int size;

  public Queue() {
    elements = new int[8];
  }

  public void enqueue(int value) {
    if (size >= elements.length) {
      int[] temp = new int[elements.length * 2];
      System.arraycopy(elements, 0, temp, 0, elements.length);
      System.out.println(elements.length);
      elements = temp;
    }

    elements[size++] = value;
  }

  public int dequeue() {
    int v = elements[0];

    // Shift all elements in the array left
    for (int i = 0; i < size - 1; i++) {
      elements[i] = elements[i + 1];
    }

    size--;

    return v;
  }

  public boolean empty() {
    return size == 0;
  }

  public int getSize() {
    return size;
  }
}

Upvotes: 1

Views: 299

Answers (3)

Sajan Chandran
Sajan Chandran

Reputation: 11487

All instance variables will be assigned a default value by the compiler if you haven't provided one. Snippet from java doc

Default value will be zero or null depending the data types.

The link also has a grid which tells you about the default values for all data types.

Local variables are variables which are used inside a method:

The compiler never assigns a default value to an uninitialized local variable. If you cannot initialize your local variable where it is declared, make sure to assign it a value before you attempt to use it. Accessing an uninitialized local variable will result in a compile-time error.

Upvotes: 0

Naman Gala
Naman Gala

Reputation: 4692

Default value is 0 for int.

And size++ and size-- is doing the changes to its value.

For more information refer: Assignment, Arithmetic, and Unary Operators

Upvotes: 5

Nick ten Veen
Nick ten Veen

Reputation: 178

size++ is equal to the statement size = size + 1, the same for size-- which does size = size - 1

Upvotes: 2

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