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466 lines (349 loc) · 16.5 KB
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import java.util.*;
public class CollectionsFramework {
// main method
public static void main(String[] args) {
//declaring an array in java
int arr[] = {10, 20, 30, 40, 50};
for(int i=0; i < arr.length; i++)
{
System.out.print(" " + arr[i]);
}
// declaring any 2d array in Java or it can be used to declare the 1d matrix using new keyword
int arr[][] = new int[2][];
// Making the above array Jagged
// First row has 3 columns
arr[0] = new int[3];
// Second row has 2 columns
arr[1] = new int[2];
// Example
int[][] arr = { { 1, 2 }, { 3, 4 } };
System.out.println(Integer.bitCount(4)); // Gives out the set bits count in 4
// Strings in Java
String s= "GeeksforGeeks";
// or String s= new String ("GeeksforGeeks");
// Returns the number of characters in the String.
System.out.println("String length = " + s.length());
// Returns the character at ith index.
System.out.println("Character at 3rd position = "
+ s.charAt(3));
// Return the substring from the ith index character
// to end of string
System.out.println("Substring " + s.substring(3));
// Returns the substring from i to j-1 index.
System.out.println("Substring = " + s.substring(2,5));
// Concatenates string2 to the end of string1.
String s1 = "Geeks";
String s2 = "forGeeks";
System.out.println("Concatenated string = " +
s1.concat(s2));
// Returns the index within the string
// of the first occurrence of the specified string.
String s4 = "Learn Share Learn";
System.out.println("Index of Share " +
s4.indexOf("Share"));
// Returns the index within the string of the
// first occurrence of the specified string,
// starting at the specified index.
System.out.println("Index of a = " +
s4.indexOf('a',3));
// Checking equality of Strings
Boolean out = "Geeks".equals("geeks");
System.out.println("Checking Equality " + out);
out = "Geeks".equals("Geeks");
System.out.println("Checking Equality " + out);
out = "Geeks".equalsIgnoreCase("gEeks ");
System.out.println("Checking Equality " + out);
//If ASCII difference is zero then the two strings are similar
int out1 = s1.compareTo(s2);
System.out.println("the difference between ASCII value is="+out1);
// Converting cases
String word1 = "GeeKyMe";
System.out.println("Changing to lower Case " +
word1.toLowerCase());
// Converting cases
String word2 = "GeekyME";
System.out.println("Changing to UPPER Case " +
word2.toUpperCase());
// Trimming the word
String word4 = " Learn Share Learn ";
System.out.println("Trim the word " + word4.trim());
// Replacing characters
String str1 = "feeksforfeeks";
System.out.println("Original String " + str1);
String str2 = "feeksforfeeks".replace('f' ,'g') ;
System.out.println("Replaced f with g -> " + str2);
// https://www.geeksforgeeks.org/how-to-learn-java-collections-a-complete-guide/
// Instantiate an ArrayList Object
// Integer is a wrapper class for
// the basic datatype int
ArrayList<Integer> intArr = new ArrayList<Integer>();
// Add elements using add() method
intArr.add(10);
intArr.add(12);
intArr.add(25);
intArr.add(19);
intArr.add(11);
intArr.add(3);
// Print the ArrayList on the console
System.out.println(intArr);
// Remove elements at index 1 and 4
intArr.remove(1);
intArr.remove(4);
// Print the ArrayList on the console
System.out.println(intArr);
// Check if intArr contains the element 25
if(intArr.contains(25))
{
System.out.println("The ArrayList contains 25");
}
else
{
System.out.println("No such element exists");
}
// Use get method to get the element at index 1
int elementAt1 = intArr.get(1);
System.out.println("The Element at index 1 now is " + elementAt1);
Collections.reverse(intArr); // reversing an arraylist
List<Integer> arr = intArr.subList(st,en); // slicing of arraylist in java List is an interface of arraylist
//-------------------------------------------------------------------------------
Vector<Integer> intVector = new Vector<Integer>();
// Print the initial size of the Vector
System.out.println("The initial size of the Vector = " + intVector.size());
System.out.println();
// Add elements using add method
intVector.add(11);
intVector.add(18);
intVector.add(1);
intVector.add(87);
intVector.add(19);
intVector.add(11);
// Print the Vector on the console
System.out.println("The Vector intVector : ");
System.out.println(intVector);
System.out.println("Size of intVector : " + intVector.size());
System.out.println();
// Remove the element at index 2
intVector.remove(2);
// Print the vector again on the console
System.out.println("The Vector intVector after removing element at 2 : ");
System.out.println(intVector);
System.out.println();
// Clear all elements of the Vector and
// Print the Vector on the console
intVector.clear();
System.out.println("The Vector intVector after using clear : ");
System.out.println(intVector);
//--------------------------------------------------------------------------------------
Stack<String> strStack = new Stack<String>();
// Add elements using the push() method
strStack.push("Stack");
strStack.push("a");
strStack.push("is");
strStack.push("This");
// The size() method gives the
// number of elements in the Stack
System.out.println("The size of the Stack is : " + strStack.size());
// The search() method is
// used to search an element
// it returns the position of
// the element
int position = strStack.search("a");
System.out.println("\nThe string 'a' is at position " + position);
System.out.println("\nThe elements of the stack are : ");
String temp;
int num = strStack.size();
for(int i = 1; i <= num; i++)
{
// peek() returns the topmost element
temp = strStack.peek();
System.out.print(temp + " ");
// pop() removes the topmost element
strStack.pop();
}
//-------------------------------------------------------------------------------------
LinkedList<String> strLinkedList = new LinkedList<String>();
// Add elements to the LinkedList using add()
strLinkedList.add("This");
strLinkedList.add("is");
strLinkedList.add("a");
strLinkedList.add("LinkedList");
// The elements are retrieved using the get() method
System.out.println("The contents of strLinkedList : ");
for(int i = 0; i < strLinkedList.size(); i++)
{
System.out.print(strLinkedList.get(i) + " ");
}
// The elements are removed using remove()
strLinkedList.remove(0);
strLinkedList.remove(1);
System.out.println("\n\nThe contents of strLinkedList after remove operation : ");
for(int i = 0; i < strLinkedList.size(); i++)
{
System.out.print(strLinkedList.get(i) + " ");
}
//----------------------------------------------------------------------------------------
PriorityQueue<Integer> intPriorityQueue = new PriorityQueue<Integer>();
// Add elements using add()
intPriorityQueue.add(17);
intPriorityQueue.add(20);
intPriorityQueue.add(1);
intPriorityQueue.add(13);
intPriorityQueue.add(87);
// Print the contents of PriorityQueue
System.out.println("The contents of intPriorityQueue : ");
System.out.println(intPriorityQueue);
// The peek() method is used to retrieve
// the head of the PriorityQueue
System.out.println("\nThe head of the PriorityQueue : " + intPriorityQueue.peek());
// The remove() method is used
// to remove a single instance
// of the specified object
intPriorityQueue.remove(17);
// Print the contents of PriorityQueue
System.out.println("\nThe contents of intPriorityQueue after removing 17 : ");
System.out.println(intPriorityQueue);
// The poll() method is used
// to retrieve and remove the
// element at the head of the PriorityQueue
Integer head = intPriorityQueue.poll();
System.out.println("\nThe head of the PriorityQueue was : " + head);
// Print the contents of PriorityQueue
System.out.println("\nThe contents of intPriorityQueue after poll : ");
System.out.println(intPriorityQueue);
//---------------------------------------------------------------------------------------
/*-----------HashSet-------------*/
// Instantiate a HashSet object named strHashSet
HashSet<String> strHashSet = new HashSet<String>();
// Add elements using add()
strHashSet.add("This");
strHashSet.add("is");
strHashSet.add("a");
strHashSet.add("HashSet");
// Create an Iterator to traverse through the HashSet
Iterator<String> hsIterator = strHashSet.iterator(); // will be Integer if it is a integer.
// Print all the elements of the HashSet
System.out.println("Contents of HashSet : ");
while(hsIterator.hasNext())
{
System.out.print(hsIterator.next() + " ");
}
/*---------LinkedHashSet----------*/
// Instantiate an object of LinkedHashSet named strLinkedHashSet
// Pass the name of the HashSet created earlier to copy all of the contents
// of the HashSet to the LinkedHashSet using a constructor
LinkedHashSet<String> strLinkedHashSet = new LinkedHashSet<String>(strHashSet);
// Create an Iterator to traverse through the LinkedHashSet
Iterator<String> lhsIterator = strLinkedHashSet.iterator();
// Print all the elements of the LinkedHashSet
System.out.println("\n\nContents of LinkedHashSet : ");
while(lhsIterator.hasNext())
{
System.out.print(lhsIterator.next() + " ");
}
//--------------------------------------------------------------------------------------
TreeSet<Integer> intTreeSet = new TreeSet<Integer>();
// Add elements using add()
intTreeSet.add(18);
intTreeSet.add(13);
intTreeSet.add(29);
intTreeSet.add(56);
intTreeSet.add(73);
// Try to add a duplicate
// Observe output as it will not be added
intTreeSet.add(18);
// Print the TreeSet on the console
System.out.println("The contents of intTreeSet : ");
System.out.println(intTreeSet);
// Remove 18 using remove()
if(intTreeSet.remove(18))
{
System.out.println("\nElement 18 has been removed");
}
else
{
System.out.println("\nNo such element exists");
}
// Try to remove a non-existent element
if(intTreeSet.remove(12))
{
System.out.println("\nElement 18 has been removed");
}
else
{
System.out.println("\nNo such element exists");
}
System.out.println();
// Print the TreeSet on the console
System.out.println("The contents of intTreeSet : ");
System.out.println(intTreeSet);
//----------------------------------------------------------------------------------
/*--------------HashMap---------------*/
// Instantiate an object of HashMap named hashMap
HashMap<Integer, String> hashMap = new HashMap<Integer, String>();
// Add elements using put()
hashMap.put(1, "This");
hashMap.put(2, "is");
hashMap.put(3, "HashMap");
// Print the HashMap contents on the console
System.out.println("Contents of hashMap : ");
System.out.print(hashMap.entrySet());
// Add a duplicate key
hashMap.put(3, "Duplicate");
// Add a duplicate value
hashMap.put(4, "This");
// Print the HashMap contents on the console
System.out.println("\nContents of hashMap after adding duplicate : ");
System.out.print(hashMap.entrySet());
/*--------------Hashtable----------------*/
// Instantiate an object of Hashtable named hashTable
Hashtable<Integer, String> hashTable = new Hashtable<Integer, String>();
// Add elements using put()
hashTable.put(11, "This");
hashTable.put(12, "is");
hashTable.put(13, "Hashtable");
// Print the Hashtable contents on the console
System.out.println("\n\nContents of hashTable : ");
System.out.print(hashTable.entrySet());
// Add a duplicate key
hashTable.put(11, "Duplicate");
// Add a duplicate value
hashTable.put(14, "is");
// Print the Hashtable contents on the console
System.out.println("\nContents of hashTable after adding duplicate : ");
System.out.print(hashTable.entrySet());
/*---------------LinkedHashMap---------------*/
// Instantiate an object of LinkedHashMap named linkedHashMape
LinkedHashMap<Integer, String> linkedHashMap = new LinkedHashMap<Integer, String>();
// Add elements using put()
linkedHashMap.put(21, "This");
linkedHashMap.put(22, "is");
linkedHashMap.put(23, "LinkedHashMap");
// Print the LinkedHashMap contents on the console
System.out.println("\n\nContents of linkedHashMap : ");
System.out.print(linkedHashMap.entrySet());
// Add a duplicate key
linkedHashMap.put(22, "Duplicate");
// Add a duplicate value
linkedHashMap.put(24, "This");
// Print the LinkedHashMap contents on the console
System.out.println("\nContents of linkedHashMap after adding duplicate : ");
System.out.print(linkedHashMap.entrySet());
//--------------------------------------------------------------------------------
// Instantiate an object of TreeMap named treeMap
TreeMap<Integer, String> treeMap = new TreeMap<Integer, String>();
// Add elements using put()
treeMap.put(1, "This");
treeMap.put(2, "is");
treeMap.put(3, "TreeMap");
// Print the contents of treeMap on the console
System.out.println("The contents of treeMap : ");
System.out.println(treeMap);
// Add a duplicate key
treeMap.put(1, "Duplicate");
// Add a duplicate value
treeMap.put(4, "is");
// Print the contents of treeMap on the console
System.out.println("\nThe contents of treeMap after adding duplicates : ");
System.out.println(treeMap);
}
}
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