Array is a linear data structure where all elements are arranged sequentially. It is a collection of elements ofsamedata type stored atcontiguous memorylocations.
public class Array{ private T[] self; private int size; @SuppressWarnings("unchecked") public Array(int size) { if (size <= 0) { throw new IllegalArgumentException("Invalid array size (must be positive): " + size); } else { this.size = size; this.self = (T[]) new Object[size]; } } }
In Core Array Class, we are going to store size of array and a general skeleton for array initialization. In constructor, we are asking for size of array and making an object and type casting it in our desired array.
public void set(T item, int index) { if (index >= this.size || index < 0) { throw new IndexOutOfBoundsException("Index Out of bounds: " + index); } else { this.self[index] = item; } }
This method is asking for an item to be stored in array and index on which item should be stored.
public T get(int index) { if (index >= this.size || index < 0) { throw new IndexOutOfBoundsException("Index Out of bounds"); } else { return self[index]; } }
Get Method asks for an index and retrives item from that index.
public void print() { for (int i = 0; i < size; i++) { System.out.println(this.self[i]+" "); } }
Print Method is just printing all members of an array in a single line with a space seperating each item between them.
Arrays but having a functionality to sort elements itself.
public class SortedArray> { private T[] array; private int size; private final int maxSize; @SuppressWarnings("unchecked") public SortedArray(int maxSize) { if (maxSize <= 0) { throw new IllegalArgumentException("Invalid array max size (must be positive): " + maxSize); } this.array = (T[]) new Comparable[maxSize]; this.size = 0; this.maxSize = maxSize; } }
In Sorted Array Class, we are going to store size of array and ask for Max size of array as well and a general skeleton for array initialization. In constructor, we are asking for Max Size of array and making an object and type casting it in our desired array.
public int length() { return this.size; } public int maxLength() { return this.maxSize; } public T get(int index) { if (index < 0 || index >= this.size) { throw new IndexOutOfBoundsException("Index out of bounds: " + index); } return this.array[index]; }
private int findInsertionPosition(T item) { int left = 0; int right = size - 1; while (left <= right) { int mid = (left + right) / 2; int cmp = item.compareTo(this.array[mid]); if (cmp < 0) { right = mid - 1; } else { left = mid + 1; } } return left; } public void insert(T item) { if (this.size >= this.maxSize) { throw new IllegalStateException("The array is already full"); } int position = findInsertionPosition(item); for (int i = size; i > position; i--) { this.array[i] = this.array[i - 1]; } this.array[position] = item; size++; }
Insert Method inserts the item on its position in sorted form.
public void delete(T item) { int index = binarySearch(item); if (index == -1) { throw new IllegalArgumentException("Unable to delete element " + item + ": the entry is not in the array"); } for (int i = index; i < size - 1; i++) { this.array[i] = this.array[i + 1]; } this.array[size - 1] = null; size--; }
private int binarySearch(T target) { int left = 0; int right = size - 1; while (left <= right) { int mid = (left + right) / 2; int cmp = target.compareTo(this.array[mid]); if (cmp == 0) { return mid; } else if (cmp < 0) { right = mid - 1; } else { left = mid + 1; } } return -1; } public Integer find(T target) { int index = binarySearch(target); return index == -1 ? null : index; }
public void traverse(Callbackcallback) { for (int i = 0; i < this.size; i++) { callback.call(this.array[i]); } }
public interface Callback{ void call(T item); }
public class UppercaseCallback implements UnsortedArray.Callback{ @Override public void call(String item) { System.out.println(item.toUpperCase()); } }
It is almost same from above
Initialization and getters are same.
public void insert(T item) { if (this.size >= this.maxSize) { throw new IllegalStateException("The array is already full"); } else { this.self[this.size] = item; this.size++; } }
Delete Method is also same
public Integer find(T target) { for (int i = 0; i < this.size; i++) { if (this.self[i].equals(target)) { return i; } } return null; }
Dynamic Array are like array lists or lists.
public class DynamicArray{ private T[] array; private int size; private int capacity; @SuppressWarnings("unchecked") public DynamicArray(int initialCapacity) { if (initialCapacity <= 0) { throw new IllegalArgumentException("Invalid initial capacity: " + initialCapacity); } this.capacity = initialCapacity; this.array = (T[]) new Object[initialCapacity]; this.size = 0; } }
private void resize(int newCapacity) { @SuppressWarnings("unchecked") T[] newArray = (T[]) new Object[newCapacity]; for (int i = 0; i < size; i++) { newArray[i] = array[i]; } array = newArray; capacity = newCapacity; } public void insert(T item) { if (size >= capacity) { resize(2 * capacity); } array[size++] = item; }
public void delete(T item) { int index = find(item); if (index == -1) { throw new IllegalArgumentException("Item not found: " + item); } for (int i = index; i < size - 1; i++) { array[i] = array[i + 1]; } array[--size] = null; if (capacity > 1 && size <= capacity / 4) { resize(capacity / 2); } }
Everything else is same.
Hope this helps in working with arrays. Good Luck!
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