Commonly asked programs in java interview

 

Permutaion of word

for ex ABC will be abc , acb,bac,bca,cab,cba

public class Permutation {

public static void main(String[] args) {

    String s=”abc”;

    List<String>combinations=new ArrayList<String>();

    combinations=permutations(s);

    System.out.println(combinations);

}

 

private static List<String> permutations(String s) {

    // TODO Auto-generated method stub

    List<String>combinations=new ArrayList<String>();

    System.out.println(s.length());

    if(s.length()==1){

        combinations.add(s);

    }

    else{

    System.out.println(“Else part”);

        for(int i=0;i<s.length();i++){

       

            List<String>temp=permutations(s.substring(0, i)+s.substring(i+1));

            for (String string : temp) {

                combinations.add(s.charAt(i)+string);

                System.out.println(“s.charAt(i)+string : “+s.charAt(i)+string);

            }

        }

    }

    return combinations;

 

}

 

}

 

Reverse Array without additional array

public class ReverseWithoutAdditionalArray {

 static void reverseArray(int inputArray[])

   {  System.out.println(“Array Before Reverse : “+Arrays.toString(inputArray));

          int temp;

         for (int i = 0; i < inputArray.length/2; i++) 

        {

            temp = inputArray[i];

              

            inputArray[i] = inputArray[inputArray.length-1-i];

              

            inputArray[inputArray.length-1-i] = temp;

        }

          

        System.out.println(“Array After Reverse : “+Arrays.toString(inputArray));

         

        System.out.println(“=========================================”);

    }

      

    public static void main(String[] args) 

    {    

        reverseArray(new int[]{4, 5, 11, 9, 10})

    }    

}

 

Separate zeros from arrays

 

public class SeparateZero {

public static void main(String[] args) {

int arr[] = {1,2,3,0,5,0,7,8,0};

int newArr[]=new int[arr.length];

int count=0;

for(int i=0;i<arr.length;i++)

{

if(arr[i] != 0)

{

newArr[count]=arr[i];

count++;

}

}

while(count < arr.length)

{

newArr[count]=0;

count++;

}

System.out.println(Arrays.toString(newArr));

}

}

Find unique elements from arrays

Unique elements

for(int i=0;i<arr.length-1;i++)

{ int count =0;

for(int j=1;j<=i;j++)

{

if(arr[i] == arr[j])

{

count++;

}

}

if(count != 1)

{System.out.println(“Duplicate”);

System.out.println(arr[i]);

}

else

{

System.out.println(“Unique”);

System.out.println(arr[i]);

}

}

Add or remove elements from array

int[] my_array = { 25, 14, 56 ,34,12,76};

// Insert an element in 3rd position of the array (index->2, value->5)

//Adding value

 

int Index_position = 2;

int newValue = 5;

System.out.println(“Original Array : ” + Arrays.toString(my_array));

for (int i = my_array.length-1; i > Index_position; i–) {

my_array[i] = my_array[i-1];

}

my_array[Index_position] = newValue;

System.out.println(“New Array: ” + Arrays.toString(my_array));

//Removing value from array

int [] arr= {5,6,7,8};

int [] newArr=new int[arr.length-1];

int j=6;

int k=0;

for(int i=0;i<arr.length;i++)

{

if(arr[i] != j)

{

newArr[k]=arr[i];

k++;

}

}

System.out.println(Arrays.toString(newArr));

 

Find missing number

 

public static void main(String[] args) {

int num[] = { 1, 2, 3, 4, 5, 6, 7, 8, 10 };

int length = num.length;

int nums = length + 1;

int sumno = sumOfNnumbers(nums);

int toatal = sumOfTotalNumber(num);

 

int missing = toatal – sumno;

System.out.println(“Missing number ” + missing * (-1));

}

 

static int sumOfNnumbers(int n) {

int sum = 0;

for (int i = 0; i <= n; i++) {

sum = sum + i;

}

return sum;

 

}

 

static int sumOfTotalNumber(int arr[]) {

int sums = 0;

for (int i = 0; i < arr.length; i++) {

sums = sums + arr[i];

}

 

return sums;

}

}

 

Find Max number from array

for(int i=0;i<arr.length-1;i++)

{

if(arr[i] > max )

{

max=arr[i];

}

}

System.out.println(“Maximum elements :”+max);

for(int i=0;i<arr.length-1;i++)

{

if(arr[i] < min )

{

min=arr[i];

}

}

 

String:

 

package in.com;

/* 

 * with predefined function

 * char[] ArrayS1 = s1.toLowerCase().toCharArray();  

            char[] ArrayS2 = s2.toLowerCase().toCharArray();  

            Arrays.sort(ArrayS1);  

            Arrays.sort(ArrayS2);  

            status = Arrays.equals(ArrayS1, ArrayS2); 

 * 

 */

public class AnagromString {

 

public static void main(String[] args) {

String str1=”Shubham chivhane”;

String Str2=”chibham Shumhaneqw”;

String s1=str1.replaceAll(“\\s”, ” “);

String s2=Str2.replaceAll(“\\s”, ” “);

 

   

  if(s1.length() == s2.length())

{

  char a1[]=s1.toLowerCase().toCharArray();

  char a2[]=s2.toLowerCase().toCharArray();

  

  for(int i=0;i<a1.length;i++)

  {

  for(int j=i+1;j<a1.length;j++)

  {

  char tmp;

  if(a1[i] > a1[j])

  {

  tmp=a1[i];

  a1[i]=a1[j];

  a1[j]=tmp;

  }

  

  }

  }

  for(int i=0;i<a2.length;i++)

  {

  for(int j=i+1;j<a2.length;j++)

  {

  char tmp;

  if(a2[i] > a2[j])

  {

  tmp=a2[i];

  a2[i]=a2[j];

  a2[j]=tmp;

  }

  

  }

  }

  if(a1.equals(a2)) {

  System.out.println(“Anagrom”);

  }

  else

  {

  System.out.println(“Not Anagrom”);

  }

}

  else

  {

  System.out.println(“Not Anagrom”);

  }

  

}

}

 

Find Number of words in string

 

public class NumberOfwords {

 

public static void main(String[] args) {

String str=”aa bb ccc dd ee”;

String [] word=str.split(” “);

System.out.println(“No of word “+ word.length);

}

 

}————————————————

 

Find Number of perticular words in string

public class NumberOfwords2 {

 

public static void main(String[] args) {

String str=”abcf ssd sds “;

char str1=’s’;

int count=0;

for(int i=0;i<str.length();i++)

{

  if(str.charAt(i)== str1)

  {

  count++;

  }

}

System.out.println(count);

}

 

Reverse String and Array

 

public class ReverseStringAndArray {

 

public static void main(String[] args) {

int arr[] = {10,20,30,40,50};

int newArr[]= new int[arr.length];

System.out.println(“before reverse Integer Array: “+Arrays.toString(newArr)); 

int j=0;

for(int i = arr.length -1;i>=0;i–)

{

//System.out.println(arr[i]);

newArr[j] = arr[i];

// System.out.println(newArr[i]);

j++;

}

System.out.println(“reverse Integer Array: “+Arrays.toString(newArr)); 

 

String str=”SHUBHAM”;

char a[]=new char[str.length()];

int k=0;

for(int i=str.length()-1;i>=0;i–)

{

a[k]=str.charAt(i);

k++;

}

System.out.println(“String before reverse: “+str); 

System.out.println(“reverse string: “+String. valueOf(a)); 

}

 

}

 

 

find word and their count

 

public class Test {

 

public static void main(String[] args) {

String str=”Bread butter and bread”;

String[] words=str.split(” “);

HashMap<String, Integer> hm = new HashMap<>();

for(String word : words)

{

if(hm.containsKey(word))

{

hm.put(word.toLowerCase(), hm.get(word)+1);

}

else

{

hm.put(word.toLowerCase(), 1);

}

}

for(Entry<String, Integer> entry : hm.entrySet())

{

System.out.println(entry.getKey() +” “+entry.getValue());

//if we want duplicate key then we can use it

// if(entry.getValue() > 1)

//

// System.out.println(“duplicate key only”);

// System.out.println(entry.getKey() +” “+entry.getValue());

// }

}

}

}