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Commit 82d6fd2

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author
Rajeev Kumar Singh
committed
Java Stack, Queue, Comparator and Comparable
1 parent 8f5b91c commit 82d6fd2

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9 files changed

+155
-7
lines changed

9 files changed

+155
-7
lines changed

‎Readme.md‎

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6. [Java HashSet Tutorial with Examples](https://www.callicoder.com/java-hashset/)
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7. [Java TreeSet Tutorial with Examples](https://www.callicoder.com/java-treeset/)
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8. [Java Stack Class Tutorial with Examples](https://www.callicoder.com/java-stack/)
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9. [Java Queue Interface Tutorial with Examples](https://www.callicoder.com/java-queue/)

‎java-comparable-comparator-examples/src/ComparableExample.java‎

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@@ -10,18 +10,18 @@ public static void main(String[] args) {
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employees.add(new Employee(1010, "Rajeev", 100000.00, LocalDate.of(2010, 7, 10)));
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employees.add(new Employee(1004, "Chris", 95000.50, LocalDate.of(2017, 3, 19)));
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employees.add(new Employee(1007, "David", 134000.00, LocalDate.of(2017, 9, 28)));
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employees.add(new Employee(1015, "David", 134000.00, LocalDate.of(2017, 9, 28)));
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System.out.println("Employees (Before Sorting) : " + employees);
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// This will use the `compareTo()` method of the `Employee` class to compare two employees and sort them.
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Collections.sort(employees);
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System.out.println("Employees (After Sorting) : " + employees);
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System.out.println("\nEmployees (After Sorting) : " + employees);
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// This will use the same `compareTo()` method of the `Employee` class but will reverse the order
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Collections.sort(employees, Comparator.reverseOrder());
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System.out.println("Employees (After Sorting with reverseOrder)" + employees);
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System.out.println("\nEmployees (After Sorting with reverseOrder)" + employees);
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}
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}

‎java-comparable-comparator-examples/src/ComparatorExample.java‎

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Collections.sort(employees, Comparator.comparing(Employee::getJoiningDate));
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System.out.println("\nEmployees (Sorted by JoiningDate) : " + employees);
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// Sort employees by descending order of Name
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// Sort employees by Name in descending order
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Collections.sort(employees, Comparator.comparing(Employee::getName).reversed());
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System.out.println("\nEmployees (Sorted by Name Descending Order) : " + employees);
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System.out.println("\nEmployees (Sorted by Name in descending order) : " + employees);
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// Chaining multiple Comparators
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// Sort by Salary. If Salary is same then sort by Name

‎java-comparable-comparator-examples/src/Employee.java‎

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import java.time.LocalDate;
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import java.util.Objects;
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class Employee implements Comparable<Employee> {
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private int id;
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return this.getId() - anotherEmployee.getId();
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}
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// Two employees are equal if their IDs are equal
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@Override
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public boolean equals(Object o) {
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if (this == o) return true;
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if (o == null || getClass() != o.getClass()) return false;
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Employee employee = (Employee) o;
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return id == employee.id;
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}
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@Override
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public int hashCode() {
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return Objects.hash(id);
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}
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@Override
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public String toString() {
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return "Employee{" +

‎java-linkedhashmap-examples/src/RemoveEntriesFromLinkedHashMapExample.java‎

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System.out.println("husbandWifeMapping : " + husbandWifeMapping);
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// Remove the entry with the given key from the LinkedHashMap
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// Remove a key from the LinkedHashMap
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String wife = husbandWifeMapping.remove("John");
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System.out.println("Removed John and his wife " + wife + " from the mapping. New husbandWifeMapping : " + husbandWifeMapping);
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// Remove the entry with the given key from the LinkedHashMap only if the key is mapped to the given value
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// Remove a key from the LinkedHashMap only if it is mapped to the given value
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boolean isRemoved = husbandWifeMapping.remove("John", "Susan");
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System.out.println("Did John get removed from the mapping? : " + isRemoved);
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}
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import java.util.LinkedList;
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import java.util.Queue;
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public class QueueExample {
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public static void main(String[] args) {
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// Create and initialize a Queue using a LinkedList
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Queue<String> waitingQueue = new LinkedList<>();
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// Adding new elements to the Queue (The Enqueue operation)
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waitingQueue.add("Rajeev");
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waitingQueue.add("Chris");
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waitingQueue.add("John");
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waitingQueue.add("Mark");
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waitingQueue.add("Steven");
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System.out.println("WaitingQueue : " + waitingQueue);
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// Removing an element from the Queue using remove() (The Dequeue operation)
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// The remove() method throws NoSuchElementException if the Queue is empty
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String name = waitingQueue.remove();
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System.out.println("Removed from WaitingQueue : " + name + " | New WaitingQueue : " + waitingQueue);
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// Removing an element from the Queue using poll()
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// The poll() method is similar to remove() except that it returns null if the Queue is empty.
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name = waitingQueue.poll();
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System.out.println("Removed from WaitingQueue : " + name + " | New WaitingQueue : " + waitingQueue);
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}
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}
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import java.util.LinkedList;
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import java.util.Queue;
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public class QueueSizeSearchFrontExample {
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public static void main(String[] args) {
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Queue<String> waitingQueue = new LinkedList<>();
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waitingQueue.add("Jennifer");
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waitingQueue.add("Angelina");
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waitingQueue.add("Johnny");
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waitingQueue.add("Sachin");
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System.out.println("WaitingQueue : " + waitingQueue);
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// Check is a Queue is empty
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System.out.println("is waitingQueue empty? : " + waitingQueue.isEmpty());
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// Find the size of the Queue
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System.out.println("Size of waitingQueue : " + waitingQueue.size());
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// Check if the Queue contains an element
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String name = "Johnny";
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if(waitingQueue.contains(name)) {
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System.out.println("WaitingQueue contains " + name);
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} else {
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System.out.println("Waiting Queue doesn't contain " + name);
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}
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// Get the element at the front of the Queue without removing it using element()
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// The element() method throws NoSuchElementException if the Queue is empty
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String firstPersonInTheWaitingQueue = waitingQueue.element();
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System.out.println("First Person in the Waiting Queue (element()) : " + firstPersonInTheWaitingQueue);
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// Get the element at the front of the Queue without removing it using peek()
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// The peek() method is similar to element() except that it returns null if the Queue is empty
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firstPersonInTheWaitingQueue = waitingQueue.peek();
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System.out.println("First Person in the Waiting Queue : " + firstPersonInTheWaitingQueue);
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}
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}
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import java.util.Stack;
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public class StackExample {
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public static void main(String[] args) {
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// Creating a Stack
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Stack<String> stackOfCards = new Stack<>();
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// Pushing new items to the Stack
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stackOfCards.push("Jack");
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stackOfCards.push("Queen");
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stackOfCards.push("King");
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stackOfCards.push("Ace");
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System.out.println("Stack => " + stackOfCards);
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System.out.println();
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// Popping items from the Stack
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String cardAtTop = stackOfCards.pop(); // Throws EmptyStackException if the stack is empty
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System.out.println("Stack.pop() => " + cardAtTop);
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System.out.println("Current Stack => " + stackOfCards);
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System.out.println();
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// Get the item at the top of the stack without removing it
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cardAtTop = stackOfCards.peek();
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System.out.println("Stack.peek() => " + cardAtTop);
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System.out.println("Current Stack => " + stackOfCards);
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}
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}
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import java.util.Stack;
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public class StackSizeSearchExample {
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public static void main(String[] args) {
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Stack<String> stackOfCards = new Stack<>();
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stackOfCards.push("Jack");
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stackOfCards.push("Queen");
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stackOfCards.push("King");
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stackOfCards.push("Ace");
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System.out.println("Stack : " + stackOfCards);
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// Check if the Stack is empty
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System.out.println("Is Stack empty? : " + stackOfCards.isEmpty());
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// Find the size of Stack
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System.out.println("Size of Stack : " + stackOfCards.size());
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// Search for an element
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// The search() method returns the 1-based position of the element from the top of the stack
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// It returns -1 if the element was not found in the stack
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int position = stackOfCards.search("Queen");
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if(position != -1) {
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System.out.println("Found the element \"Queen\" at position : " + position);
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} else {
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System.out.println("Element not found");
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}
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}
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}

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