Remove duplicates from arraylist without using collections

java Collections interview Questions

1.Write a Java program to remove duplicate elements from an arraylist without using collections (without using set)

1. package arrayListRemoveduplicateElements;
2. import java.util.ArrayList;
3.  
4. public class RemoveDuplicates {
6. public static void main(String[] args){
7.     
8.     ArrayList<Object> al = new ArrayList<Object>();
9.     
10.     al.add("java");
11.     al.add('a');
12.     al.add('b');
13.     al.add('a');
14.     al.add("java");
15.     al.add(10.3);
16.     al.add('c');
17.     al.add(14);
18.     al.add("java");
19.     al.add(12);
20.     
21. System.out.println("Before Remove Duplicate elements:"+al);
22.  
23. for(int i=0;i<al.size();i++){
24.  
25.  for(int j=i+1;j<al.size();j++){
26.             if(al.get(i).equals(al.get(j))){
27.                 al.remove(j);
28.                 j--;
29.             }
30.     }
31.  
32.  }
33.  
34.     System.out.println("After Removing duplicate elements:"+al);
35.  
36. }
39.  
40. }

Output:

1. Before Remove Duplicate elements:[java, a, b, a, java, 10.3, c, 14, java, 12]
2. After Removing duplicate elements:[java, a, b, 10.3, c, 14, 12]

2. Write a Java program to remove duplicate elements from an array using Collections (Linkedhashset)

1. package arrayListRemoveduplicateElements;
2.  
3. import java.util.ArrayList;
4. import java.util.HashSet;
5. import java.util.List;
6.  
7. public class RemoveDuplicates {
9.  
10. public static void main(String[] args){
11.     
12.     List<String>  arraylist = new ArrayList<String>();
13.     
14.     arraylist.add("instanceofjava");
15.     arraylist.add("Interview Questions");
16.     arraylist.add("Interview Programs");
17.     arraylist.add("java");
18.     arraylist.add("Collections Interview Questions");
19.     arraylist.add("instanceofjava");
20.     arraylist.add("Java Experience Interview Questions");
21.     
22.     
23.     System.out.println("Before Removing duplicate elements:"+arraylist);
24.     
25.     HashSet<String> hashset = new HashSet<String>();
26.     
27.     /* Adding ArrayList elements to the HashSet
28.      * in order to remove the duplicate elements and 
29.      * to preserve the insertion order.
30.      */
31.     hashset.addAll(arraylist);
32.  
33.     // Removing ArrayList elements
34.     arraylist.clear();
35.  
36.     // Adding LinkedHashSet elements to the ArrayList
37.     arraylist.addAll(hashset );
38.  
39.     System.out.println("After Removing duplicate elements:"+arraylist);
40.  
41. }
44.  
45. }

Output:
 

1. Before Removing duplicate elements:[instanceofjava, Interview Questions, Interview
2. Programs, java, Collections Interview Questions, instanceofjava, Java Experience Interview
3. Questions]
4. After Removing duplicate elements:[java, Collections Interview Questions, Java Experience
5. Interview Questions, Interview Questions, instanceofjava, Interview Programs]

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Remove duplicates from arraylist without using collections

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