1. Write a Java program to implement a stack using arrays.

2. Write a Java program to implement a queue using arrays.

3. Write a Java program to implement a circular queue.

4. Write a Java program to implement a linked list.

5. Write a Java program to implement a doubly linked list.

6. Write a Java program to implement a binary search tree.

7. Write a Java program to perform in-order, pre-order, and post-order traversal on a binary tree.

8. Write a Java program to find the height of a binary tree.

9. Write a Java program to count the number of leaf nodes in a binary tree.

10. Write a Java program to check if two binary trees are identical.

11. Write a Java program to perform a binary search.

12. Write a Java program to implement a hash table with linear probing.

13. Write a Java program to implement a hash table with separate chaining.

14. Write a Java program to find the shortest path in a graph using Dijkstra's algorithm.

15. Write a Java program to detect a cycle in a graph.

16. Write a Java program to implement a depth-first search (DFS) on a graph.

17. Write a Java program to implement a breadth-first search (BFS) on a graph.

18. Write a Java program to find the longest common subsequence (LCS) of two strings.

19. Write a Java program to solve the knapsack problem using dynamic programming.

20. Write a Java program to solve the coin change problem using dynamic programming.

21. Write a Java program to implement the quicksort algorithm.

22. Write a Java program to implement the mergesort algorithm.

23. Write a Java program to implement the heapsort algorithm.

24. Write a Java program to implement the counting sort algorithm.

25. Write a Java program to implement the radix sort algorithm.

26. Write a Java program to find the kth largest element in an array.

27. Write a Java program to rotate a matrix by 90 degrees.

28. Write a Java program to find the transpose of a matrix.

29. Write a Java program to multiply two matrices.

30. Write a Java program to find the determinant of a matrix.

31. Write a Java program to solve a Sudoku puzzle using backtracking.

32. Write a Java program to implement a priority queue using a heap.

33. Write a Java program to find the median of a data stream.

34. Write a Java program to implement a trie (prefix tree).

35. Write a Java program to find the longest palindromic substring in a string.

36. Write a Java program to find the minimum number of steps to convert one string to another using edit distance.

37. Write a Java program to generate all permutations of a string.

38. Write a Java program to find the maximum subarray sum using Kadane's algorithm.

39. Write a Java program to find the majority element in an array.

40. Write a Java program to find the common elements in three sorted arrays.

41. Write a Java program to find the intersection of two arrays.

42. Write a Java program to find the union of two arrays.

43. Write a Java program to find the first missing positive integer in an array.

44. Write a Java program to find the subarray with the given sum.

45. Write a Java program to sort a nearly sorted (or K-sorted) array.

46. Write a Java program to find the smallest and second smallest elements in an array.

47. Write a Java program to implement a LRU cache.

48. Write a Java program to find the minimum spanning tree of a graph using Kruskal's algorithm.

49. Write a Java program to find the minimum spanning tree of a graph using Prim's algorithm.

50. Write a Java program to implement a basic calculator to evaluate a simple expression string.