Check Validate User

class UserDAO {
     
    public static String[]  getUsers() {
        String [] usernames = new String[] { "sridhar", "senthil", "siva" , "kamal" };
        return usernames;
    }
     
    public static boolean isValidUser(String username) {
         
        String[] users = getUsers();
        boolean isValid = false;
        for (String name : users) {
             
            if ( name.equals(username )) {
                isValid = true;
                break;
            }
        }
         
        return isValid;
         
    }
}
 
 
public class TestLogin {
 
    public static void main(String[] args) {
         
        //success case
        String username1 = "sridhar";
        System.out.println(  username1 + " is a Valid User ? " +  UserDAO.isValidUser(username1));
         
        //failure case
        String username2 = "abc";
        System.out.println(  username2 + " is a Valid User ? " +  UserDAO.isValidUser(username2));
         
    }
}

Sorting an array element

import java.util.Arrays;
public class SortArray {
 
    public static void main(String... args)
    {
            String[] states = {"Tamilnadu","Andra pradesh","Karnataka","Kerala","Delhi"};
 
            Arrays.sort(states); // States array values will be sorted here
 
            for(int i=0;i<states.length;i++)
            {
                System.out.println("States : "+states[i]);
            }
    }
}

Array of Objects

GradeUtil.java

---

 

package com.array.gradeapp;

public class GradeUtil {
	public String calcGrade(int mark) {
		String grade = null;
		if (mark > 100) {
			System.out.println("\n Invalid Entry");
		} else {
			if ((mark >= 90) && (mark <= 100)) {
				grade = "S";
			}
			if ((mark <= 89) && (mark >= 80)) {
				grade = "A";
			}
			if ((mark >= 70) && (mark <= 79)) { 				grade = "B"; 			} 			if ((mark >= 60) && (mark <= 69)) { 				grade = "C"; 			} 			if ((mark >= 50) && (mark <= 59)) { 				grade = "D"; 			} 			if ((mark >= 40) && (mark <= 49)) {
				grade = "E";
			}

			if (mark < 40) {
				grade = "F";
			}

		}
		return (grade);
	}
}

Student.java

---

 

package com.array.gradeapp;

public class Student {
	String name;
	int mark;

	public Student(String name, int mark) {
		super();
		this.name = name;
		this.mark = mark;
	}
	public String getName() {
		return name;
	}
	public int getMark() {
		return mark;
	}

	public String getGrade()
	{
		GradeUtil studentGrade= new GradeUtil();
		String grade = studentGrade.calcGrade(this.getMark());
		return grade;
	}
}

TestGradeApp.java

---

 

package com.array.gradeapp;

public class TestGradeApp {

	public static void main(String[] args) {
		Student student1 = new Student("Karthik", 80);
		Student student2 = new Student("Sridhar", 74);
		Student student3 = new Student("Arun", 45);

		Student[] students = new Student[5];
		students[0]=student1;
		students[1]=student2;
		students[2]=student3;

		for(Student student: students)
		{
			if(student!=null)
			{
				String grade=student.getGrade();
				System.out.println("Name :"+student.getName()+", Mark :"+student.getMark() +", Grade :"+grade);
			}
		}
	}
}

Inserting and Shifting an Element in an Array

package com.sridhar.array;

import java.util.Scanner;

public class TestArrayOperations {

	public static void main(String[] args) {
		int[] myArray = new int[5];
		myArray[0]=1;
		myArray[1]=2;
		myArray[2]=3;
		//Array Iteration - Before Insertion
		for(int i=0;i<myArray.length;i++)
		{
			System.out.println(myArray[i]);
		}

		Scanner input = new Scanner(System.in);
		System.out.println("Enter the position to insert");
		int insPosition = input.nextInt();
		System.out.println("Enter an integer value to insert");
		int value = input.nextInt();

		//Business logic to insert an element and shifting the position by one
		myArray = doInsert(insPosition,value, myArray);

		//Array Iteration - After Insertion
		for(int i=0;i<myArray.length;i++)
		{
			System.out.println(myArray[i]);
		}

		input.close();
	}

	public static int[] doInsert(int insPosition, int valueToBeInserted, int[] myArray)
	{

		for(int i=0;i<myArray.length;i++)
		{
			if(i==insPosition)
			{
				//shifting the elements in to the next position
				for(int j=myArray.length-2;j>=insPosition;j--)
				{
					int temp=myArray[j];
					myArray[j+1] = temp;
				}
				myArray[i]=valueToBeInserted;
			}
		}
		return myArray;
	}
}