Remove duplicate elements in ArrayList without using HashSet

Question

My logic is corrupted. I'm just trying to work out a way to remove duplicates in an ArrayList without using a HashSet.

public static void main(String[] args) { ArrayList<String> wordDulicate = new ArrayList<String>(); wordDulicate.add("Tom"); wordDulicate.add("Jones"); wordDulicate.add("Sam"); wordDulicate.add("Jamie"); wordDulicate.add("Robie"); wordDulicate.add("Helen"); wordDulicate.add("Tom"); wordDulicate.add("Troy"); wordDulicate.add("Mika"); wordDulicate.add("Tom"); for (String dupWord : wordDulicate) { if (wordDulicate.equals(dupWord)) System.out.println(wordDulicate.get(dupWord)); } } 

Answer 1

This methodology requires a different list:

  ArrayList<String> wordDulicate = new ArrayList<String>(); wordDulicate.add("Tom"); wordDulicate.add("Jones"); wordDulicate.add("Sam"); wordDulicate.add("Jamie"); wordDulicate.add("Robie"); wordDulicate.add("Helen"); wordDulicate.add("Tom"); wordDulicate.add("Troy"); wordDulicate.add("Mika"); wordDulicate.add("Tom"); ArrayList<String> nonDupList = new ArrayList<String>(); Iterator<String> dupIter = wordDulicate.iterator(); while(dupIter.hasNext()) { String dupWord = dupIter.next(); if(nonDupList.contains(dupWord)) { dupIter.remove(); }else { nonDupList.add(dupWord); } } System.out.println(nonDupList); 

Output:

 [Tom, Jones, Sam, Jamie, Robie, Helen, Troy, Mika] 

Answer 2

You can create another list and add items to it, skipping duplicates: -

 ArrayList<String> wordDulicate = new ArrayList<String>(); ArrayList<String> tempList= new ArrayList<String>(); wordDulicate.add("Tom"); wordDulicate.add("Jones"); wordDulicate.add("Sam"); for (String dupWord : wordDulicate) { if (!tempList.contains(dupWord)) { tempList.add(dupWord); } } 

Answer 3

You must sort the list and delete the item that matches the previous one.

Answer 4

 import java.util.ArrayList; import java.util.LinkedList; import java.util.List; public class ArrayListDuplicateRemove { public static void main(String[] args) { List<String> lst = new LinkedList<String>(); lst.add("ABC"); lst.add("ABC"); lst.add("ABCD"); lst.add("ABCD"); lst.add("ABCE"); System.out.println("Duplicates List "+lst); Object[] st = lst.toArray(); for (Object s : st) { if (lst.indexOf(s) != lst.lastIndexOf(s)) { lst.remove(lst.lastIndexOf(s)); } } System.out.println("Distinct List "+lst); } } 

Answer 5

 package arraylist; import java.util.ArrayList; import java.util.Iterator; class Student{ String name; String dob; public Student(String name, String dob) { super(); this.name = name; this.dob = dob; } public String getName() { return name; } public void setName(String name) { this.name = name; } public String getDob() { return dob; } public void setDob(String dob) { this.dob = dob; } public String toString() { return name+"\t"+dob; } } public class RemoveDuplicate { public static void main(String[] args) { ArrayList<Student> list=new ArrayList<Student>(); list.add(new Student("prakash", "89")); list.add(new Student("prakash", "89")); list.add(new Student("saurabh", "79")); list.add(new Student("saurabh", "79")); Iterator<Student> it=list.iterator(); while(it.hasNext()){ System.out.println(it.next()); } int size=list.size(); for(int i=0;i<size-1;i++){ for(int j=i+1;j<size-1;j++){ if(list.get(i).getName().equals(list.get(j).getName())){ list.remove(j); } } } System.out.println(list); } } 

Answer 6

  ArrayList l1 = new ArrayList(); ArrayList l2 = new ArrayList(); Iterator iterator = l1.iterator(); while (iterator.hasNext()) { YourClass o = (YourClass) iterador.next(); if(!l2.contains(o)) l2.add(o); } 

l1 is the source list, and l2 is the list without duplicate elements (make sure YourClass has an equals method according to what you want to express for equality)

Answer 7

It seems a bit late for the party, but with one arraist,

Here is the code without hashset ...

 strings = new ArrayList<>(); strings.add("a1"); strings.add("a2"); strings.add("ss"); strings.add("asd"); strings.add("asd"); strings.add("a1"); strings.add("ss"); strings.add("ss"); System.out.println(Collections.frequency(strings, "ss")); for(int i = 0; i< strings.size();i++){ int frequency = Collections.frequency(strings, strings.get(i)); if(frequency>1){ String string = strings.get(i); for(int j = 1 ; j < frequency ; j++) strings.remove(string); } } System.out.println(Collections.frequency(strings, "ss")); System.out.println(strings); 

Answer 8

 ArrayList<Integer> al = new ArrayList<Integer>(); Scanner sc = new Scanner(System.in); for(int i=0;true;i++){ System.out.println("Enter your Element:"); String s1= sc.nextLine(); if(s1.equals("Exit")){ break; } int x1= Integer.parseInt(s1); al.add(x1); for(int j=0;j<al.size();j++){ for(int k=j+1;k<al.size();k++){ int temp; if(al.get(j).intValue()>al.get(k).intValue()){ temp =al.get(j).intValue(); al.set(j, al.get(k).intValue()); al.set(k, temp); }//if }//for }//for }//for System.out.println(al);