ArrayList - Integer Manipulation

// ArrayList

// Integer Array

/*

Write a Java program to perform the following task.

Take an integer array of size 20, initialize values randomly between 10 and 90, simultaneously sum all values and calculate average. Now separate values below average and above average in ArrayLists. Finally print both lists in 2 separate rows.

*/

import java.util.*;

class ALRandInt

{

     public static void main(String as[])

     {

          Integer [] ia = new Integer[20];

          ArrayList <Integer>al1 = new ArrayList<Integer>();

          ArrayList <Integer>al2 = new ArrayList<Integer>();

         

          int i = 0;

          int Sum = 0;

          while(i<20)

          {

              int v=((int)(Math.random()*1000))%90;

              if(v>10)

              {

                   ia[i]=v;

                   Sum+=v;

                   i++;

              }

          }  

         

          int avg = (int)(Sum/20);

             

          for(Integer val:ia)

          {

              int x = Integer.valueOf(val);

              if(x>avg)

                   al1.add(val);

              else

                   al2.add(val);

          }

             

          ArrayList<Integer> al = new ArrayList<>(Arrays.asList(ia));

         

          System.out.println("ArrayList 1 - All Elements : "+al);

             

          System.out.println("Average = "+avg);      

             

          System.out.println("ArrayList 2 - Elements which are above average : "+al1);

             

          System.out.println("ArrayList 3 - Elements which are below average : "+al2);

     }

}

/*

Sample Output

D:\oopjava>javac ALRandInt.java

D:\oopjava>java ALRandInt

ArrayList 1 - All Elements : [12, 84, 68, 79, 30, 66, 67, 11, 30, 82, 56, 37, 43, 49, 48, 72, 21, 56, 35, 21]

Average = 48

ArrayList 2 - Elements which are above average : [84, 68, 79, 66, 67, 82, 56, 49, 72, 56]

ArrayList 3 - Elements which are below average : [12, 30, 11, 30, 37, 43, 48, 21, 35, 21]

D:\oopjava>java ALRandInt

ArrayList 1 - All Elements : [60, 66, 39, 44, 23, 28, 70, 42, 71, 85, 31, 65, 71, 31, 59, 18, 76, 58, 86, 88]

Average = 55

ArrayList 2 - Elements which are above average : [60, 66, 70, 71, 85, 65, 71, 59, 76, 58, 86, 88]

ArrayList 3 - Elements which are below average : [39, 44, 23, 28, 42, 31, 31, 18]

D:\oopjava>

*/

ArrayList - Converting ArrayList to String Array

// ArrayList

// ArrayList to String array

/*

Write a java program to convert ArrayList to String array

*/

import java.util.*;

class ALtoSA

{

     public static void main(String as[])

     {

          // Creating ArrayList

          ArrayList <String>al = new ArrayList<String>();

          Scanner s = new Scanner(System.in);

         

          System.out.print("Enter number of strings : ");

          int N = s.nextInt();

         

          for(int i=0;i<N;i++)

          {

              System.out.print("Enter string : "); 

              String str = s.next();

              al.add(str);

          }

         

          System.out.println("Elements in ArrayList are : "+al);      

         

          // Creating a String array

          String[] SA = new String[al.size()];

         

          // Converting ArrayList to String Array

          SA = al.toArray(SA);

         

          System.out.println("Elements in String array : ");

          for(String str:SA)

              System.out.println(str);

     }

}

ArrayList - converting string array to ArrayList

// ArrayList

// String array to ArrayList

/*

Write a java program to convert String array to ArrayList

*/

import java.util.*;

class SAtoAL

{

     public static void main(String as[])

     {

          // Creating a String array

          String[] SA = new String[]{"CSE", "IT","ECE","ECE"};

         

          // Converting string array to ArrayList

          ArrayList<String> al = new ArrayList<>(Arrays.asList(SA));

         

          System.out.println("Elements in ArrayList are : "+al);

     }

}

ArrayList - String operations

/*

     Write a program to perform string operations using Array List.

     Write functions for the following

          Append - add at end

          Insert – add at particular index

          Search

          List all string starts with given letter

*/

// ArrayList

import java.util.*;

class ArrList

{

     public static void main(String as[])

     {

          ArrayList <String>AL = new ArrayList<String>();

          Scanner s = new Scanner(System.in);

         

          while(true)

          {

              System.out.println("\n1 - Append \t2 - Insert \t3 - Search \t4 - List \t5 - exit");

             

              int ch;

              System.out.print("Enter choice : "); 

              ch = s.nextInt();

              if(ch==1)

              {

                   System.out.print("Enter data : ");

                   String str = s.next();

                  

                   AL.add(str);

              }

              else if(ch==2)

              {

                   System.out.print("Enter position : ");

                   int pos = s.nextInt();

                   System.out.print("Enter data : ");

                   String str = s.next();

                   AL.add(pos,str);

              }

              else if(ch==3)

              {

                   int i;

                   System.out.print("Enter data to search : ");

                   String str = s.next();

                  

                   String str_arr[] = new String[AL.size()];

                   str_arr = AL.toArray(str_arr);             

                  

                   for(i=0;i<AL.size();i++)

                        if(str.equalsIgnoreCase(str_arr[i]))

                        {

                             System.out.println("String "+str+" found at position "+(i+1));

                             break;

                        }

                   if(i==AL.size())

                        System.out.println("String not found.");

              }

              else if(ch==4)

              {

                   System.out.println("Elements in ArrayList are : "+AL);

                  

                   int i;

                   System.out.print("Enter starting character : ");

                   char c = (s.next()).charAt(0);

                  

                  

                   String str_arr[] = new String[AL.size()];

                   str_arr = AL.toArray(str_arr);             

                   System.out.println("String atarting with character "+c+" are : ");

                   for(i=0;i<AL.size();i++)

                        if(str_arr[i].charAt(0)==c)

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

              }

              else if(ch==5)

                   System.exit(0);

              else

                   System.out.println("Invalid choice");

          }

     }

}

ArrayList - String read and display

// ArrayList

// Strings

/*

Write a java program which stores the list of strings in an ArrayList and then displays the contents of the list.

*/

// ArrayList

import java.util.*;

class AL_Str

{

     public static void main(String as[])

     {

          ArrayList <String>al = new ArrayList<String>();

          Scanner s = new Scanner(System.in);

         

          System.out.print("Enter number of strings : ");

          int N = s.nextInt();

         

          for(int i=0;i<N;i++)

          {

              System.out.print("Enter string : "); 

              String str = s.next();

              al.add(str);

          }

         

          System.out.println("Elements in ArrayList are : "+al);

     }

}