JAVA EXAMPLE PROGRAMS

JAVA EXAMPLE PROGRAMS

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Program: Write a program to find perfect number or not.


Description:
A perfect number is a positive integer that is equal to the sum
of its proper positive divisors, that is, the sum of its positive
divisors excluding the number itself. Equivalently, a perfect number
is a number that is half the sum of all of its positive divisors.
The first perfect number is 6, because 1, 2 and 3 are its proper
positive divisors, and 1 + 2 + 3 = 6. Equivalently, the number 6
is equal to half the sum of all its positive divisors:
		( 1 + 2 + 3 + 6 ) / 2 = 6.

Code:
package com.java2novice.algos;

public class IsPerfectNumber {

	public boolean isPerfectNumber(int number){
		
		int temp = 0;
		for(int i=1;i<=number/2;i++){
			if(number%i == 0){
				temp += i;
			}
		}
		if(temp == number){
			System.out.println("It is a perfect number");
			return true;
		} else {
			System.out.println("It is not a perfect number");
			return false;
		}
	}
	
	public static void main(String a[]){
		IsPerfectNumber ipn = new IsPerfectNumber();
		System.out.println("Is perfect number: "+ipn.isPerfectNumber(28));
	}
}

Output:
28
It is a perfect number
Is perfect number: true
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List Of All Interview Programs:

  1. Find out duplicate number between 1 to N numbers.
  2. Find out middle index where sum of both ends are equal.
  3. Write a singleton class.
  4. Write a program to create deadlock between two threads.
  5. Write a program to reverse a string using recursive algorithm.
  6. Write a program to reverse a number.
  7. Write a program to convert decimal number to binary format.
  8. Write a program to find perfect number or not.
  9. Write a program to implement ArrayList.
  10. Write a program to find maximum repeated words from a file.
  11. Wrie a program to find out duplicate characters in a string.
  12. Write a program to find top two maximum numbers in a array.
  13. Write a program to sort a map by value.
  14. Write a program to find common elements between two arrays.
  15. How to swap two numbers without using temporary variable?
  16. Write a program to print fibonacci series.
  17. Write a program to find sum of each digit in the given number using recursion.
  18. Write a program to check the given number is a prime number or not?
  19. Write a program to find the given number is Armstrong number or not?
  20. Write a program to convert binary to decimal number.
  21. Write a program to check the given number is binary number or not?
  22. Write a program for Bubble Sort in java.
  23. Write a program for Insertion Sort in java.
  24. Write a program to implement hashcode and equals.
  25. How to get distinct elements from an array by avoiding duplicate elements?
  26. Write a program to get distinct word list from the given file.
  27. Write a program to get a line with max word count from the given file.
  28. Write a program to convert string to number without using Integer.parseInt() method.
  29. Write a program to find two lines with max characters in descending order.
  30. Write a program to find the sum of the first 1000 prime numbers.
  31. Find longest substring without repeating characters.
  32. Write a program to remove duplicates from sorted array.
Knowledge Centre
Class, Constructor and Primitive data types
Class is a template for multiple objects with similar features and it is a blue print for objects. It defines a type of object according to the data the object can hold and the operations the object can perform. Constructor is a special kind of method that determines how an object is initialized when created. Primitive data types are 8 types and they are: byte, short, int, long, float, double, boolean, char.

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Reference: Java™ Platform Standard Ed. 7 - API Specification | Java is registered trademark of Oracle.
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