150 - Most Important Sample Programs Resolved

1) Write a java program to remove all white spaces from a given string. Answer

   
 public void replaceWhiteSpaceMethod1(String str) {

  // Method 1
  System.out.println(str.replaceAll(" ", ""));

  // Method2
  char[] arr = str.toCharArray();

  for (char c : arr) {
   if (c != ' ')
    System.out.print(c);
  }

 }

2)write a java program to find duplicate characters and their count in a given string? For example, in a string “Better Butter”, duplicate characters and their count is t : 4, e : 3, r : 2 and B : 2. Answer

   
    public void findTheNumberOfDublicates(String str){
     Map hm = new HashMap();
     char[] arr = str.toCharArray();
     for(char c : arr){
      
      if(hm.containsKey(c)){
      int val = hm.get(c);
      hm.put(c, (val+1));
      }else{
       hm.put(c, 1);
      }
     }
     
     System.out.println(hm);
        Set s = hm.entrySet();
       Iterator i = s.iterator();
       
       while(i.hasNext()){
        Map.Entry me = (Map.Entry)i.next();
           System.out.print(me.getKey() + ": "+me.getValue() +",");
   
       }
         for(Entry e: hm.entrySet()){
        System.out.print(e.getKey() + " "+e.getValue()+",");
       }
    }

3)Given an Integer array and target, write a function to return the number of pairs such that the sum of pair = target.Answer
4) Get the Number of Duplicate Elements in the List . Answer

   
    
/*Given int a[]={3,6,6,3,9,3,5,7,2,5}; and target 12. Sum of pairs equals 12 is below

{(6,6) (6,6) (3,9) (9,3) (5,7) (7,5) } . Pair (3,9) and (9,3) will be treated same so answer is 3.*/

public class SumOfPairs {

 public static void main(String[] args) {
  // TODO Auto-generated method stub
  int target = 12;
  int a[]={3,6,6,3,9,3,5,7,2,5};
  SumOfPairs obj = new SumOfPairs();
  System.out.println(obj.pairs(a, target));  

 }  
 public int pairs(int[] a, int target){
  
  int flag =0;
  ArrayList> al = new ArrayList>();  
  for(int i=0;i pair = new ArrayList();
    ArrayList repair = new ArrayList();
    pair.add(a[i]);
    pair.add(a[i+1]);
    repair.add(a[i+1]);
    repair.add(a[i]);
    if(al.contains(pair)||al.contains(repair)){
     
    }else{
     al.add(pair);    
     al.add(repair);
     flag++;
     
    } 
   }
  }
 
  for(int i=0;i