HashTablePractice.java

package com.company;

import java.util.HashMap;
import java.util.HashSet;
import java.util.Hashtable;
import java.util.Map;

public class HashTablePractice {

    public static void main(String[] args) {
        Hashtable<Integer, String> mTable = new Hashtable<>();

        mTable.put(1, "computer");
        mTable.put(2, "keyboard");
        mTable.put(3, "Laptop");
        mTable.put(4, "Monitor");
        mTable.put(5, "Printer");


        System.out.println(mTable.get(3));

        mTable.put(5, "Mobile");
        System.out.println(mTable);

        System.out.println(mTable.getOrDefault(6, "Not found"));

        Map<Integer, Student> studentHashtable = new Hashtable<>();


       /* boolean m =mTable.contains(true);

        System.out.println(m);*/

        studentHashtable.put(1, new Student("Sayeed", 23));
        studentHashtable.put(2, new Student("Sayeed", 23));
        studentHashtable.put(3, new Student("Robin", 23));


        for (Map.Entry<Integer, Student> mapEntry: studentHashtable.entrySet()) {

            System.out.println(mapEntry);
        }


        HashMap<Integer,String> hashMap = new HashMap<>();
        hashMap.put(34,"sdfi");
        hashMap.put(null,null);
        hashMap.put(12,null);
        hashMap.put(12,"isdf");
        hashMap.put(14,null);
        hashMap.put(166,null);
        hashMap.put(16,null);
        System.out.println(hashMap);


        HashSet<Student> mNumber = new HashSet<>();
        mNumber.add(new Student("Sayeed",23));
        mNumber.add(new Student("Sayeed",23));
        mNumber.add(new Student("Sayeed",23));
        mNumber.add(new Student("Sayeed",23));


        for (Student mValue: mNumber) {
            System.out.println(mValue);
        }
    }
}

Main.java

package com.company;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;

public class Main {

    public static void main(String[] args) {
        // write your code here
        /**
         * ArrayList =  Dynamic Array
         */

        ArrayList<Integer> numbers = new ArrayList();
        ArrayList<Student> studentArrayList = new ArrayList<>();
        ArrayList<String> textList = new ArrayList<>();
        ArrayList<Boolean> booleans = new ArrayList<>();

        numbers.add(2);
        studentArrayList.add(new Student("Sayeed", 23));
        textList.add("Isdfs");
        booleans.add(true);

        numbers.add(4);
        studentArrayList.add(new Student("Bappi", 23));
        textList.add("Isdfs");
        booleans.add(true);

        numbers.add(5);
        studentArrayList.add(new Student("Masum", 23));
        textList.add("Isdfs");
        booleans.add(true);

        numbers.add(7);
        studentArrayList.add(new Student("Rafi", 23));
        textList.add("Isdfs");
        booleans.add(true);

        numbers.add(88);
        studentArrayList.add(new Student("Robin", 23));
        textList.add("Isdfs");
        booleans.add(true);

        numbers.add(9);
        studentArrayList.add(new Student("Ekanto", 23));
        textList.add("Isdfs");
        booleans.add(true);

        System.out.println(Arrays.toString(studentArrayList.toArray()));
        Student student = studentArrayList.get(2);
        //  System.out.println(student);
        // studentArrayList.remove(student);
        System.out.println(Arrays.toString(studentArrayList.toArray()));
        boolean isDelete = studentArrayList.remove(student);

        ArrayList<Student> mStudentList = new ArrayList<>();

        mStudentList.add(new Student("Inan", 12));
        mStudentList.add(new Student("Sayeed", 66));
        mStudentList.add(new Student("Ruj", 9));
        mStudentList.add(new Student("Robin", 13));
        mStudentList.add(new Student("Arif", 60));

        //    Collections.reverse(mStudentList);
        Collections.sort(mStudentList, new NameComparator());
        System.out.println(mStudentList);
        //   studentArrayList.addAll(mStudentList);

        for (Student mStudent : studentArrayList) {
            //     System.out.println(mStudent);
        }

        try {
            Student student1 = mStudentList.get(1);
            System.out.println(student1);
        } catch (Exception e) {
            System.out.println(e.getMessage());
        } finally {
            System.out.println("Finally executed");
        }

        int n = 100 / 2;
        if (n == 50) {
            throw new ArithmeticException("not valid");
        }

    }
}

NameComparator.java

package com.company;

import java.util.Comparator;

public class NameComparator implements Comparator<Student> {
    @Override
    public int compare(Student student, Student t1) {

       /* if(student.getAge()==t1.getAge())
            return 0;
        else if(student.getAge()>t1.getAge())
            return 1;
        else
            return -1;*/
       return student.getName().compareTo(t1.getName());
    }
}

Student.java

package com.company;

import java.util.Objects;

public class Student {

    private String name;
    private int age;

    public Student(String name, int age) {
        this.name = name;
        this.age = age;
    }

    @Override
    public String toString() {
        return "{" + this.name + " " + this.age + "}";
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        Student student = (Student) o;
        return Objects.equals(name, student.name) &&
                Objects.equals(age, student.age);
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    @Override
    public int hashCode() {
        return Objects.hash(name, age);
    }

    /*@Override
    public int compareTo(Object o) {
        if (o instanceof Student) {
            if (((Student) o).age == this.age)
                return 0;
            else if (((Student) o).age > this.age)
                return -1;
            else if (((Student) o).age < this.age)
                return 1;
        }
        return 0;
    }*/
}