How to remove element from ArrayList by checking its value?

I have ArrayList, from which I want to remove an element which has particular value...

for eg.

ArrayList<String> a=new ArrayList<String>(); a.add("abcd"); a.add("acbd"); a.add("dbca"); 

I know we can iterate over arraylist, and .remove() method to remove element but I dont know how to do it while iterating. How can I remove element which has value "acbd", that is second element?

11 Answers

In your case, there's no need to iterate through the list, because you know which object to delete. You have several options. First you can remove the object by index (so if you know, that the object is the second list element):

 a.remove(1); // indexes are zero-based 

Or, you can remove the first occurence of your string:

 a.remove("acbd"); // removes the first String object that is equal to the // String represented by this literal 

Or, remove all strings with a certain value:

 while(a.remove("acbd")) {} 

It's a bit more complicated, if you have more complex objects in your collection and want to remove instances, that have a certain property. So that you can't remove them by using remove with an object that is equal to the one you want to delete.

In those case, I usually use a second list to collect all instances that I want to delete and remove them in a second pass:

 List<MyBean> deleteCandidates = new ArrayList<>(); List<MyBean> myBeans = getThemFromSomewhere(); // Pass 1 - collect delete candidates for (MyBean myBean : myBeans) { if (shallBeDeleted(myBean)) { deleteCandidates.add(myBean); } } // Pass 2 - delete for (MyBean deleteCandidate : deleteCandidates) { myBeans.remove(deleteCandidate); } 

One-liner (java8):

list.removeIf(s -> s.equals("acbd")); // removes all instances, not just the 1st one 

(does all the iterating implicitly)

You would need to use an Iterator like so:

Iterator<String> iterator = a.iterator(); while(iterator.hasNext()) { String value = iterator.next(); if ("abcd".equals(value)) { iterator.remove(); break; } } 

That being said, you can use the remove(int index) or remove(Object obj) which are provided by the ArrayList class. Note however, that calling these methods while you are iterating over the loop, will cause a ConcurrentModificationException, so this will not work:

for(String str : a) { if (str.equals("acbd") { a.remove("abcd"); break; } } 

But this will (since you are not iterating over the contents of the loop):

a.remove("acbd"); 

If you have more complex objects you would need to override the equals method.

for java8 we can simply use removeIf function like this

listValues.removeIf(value -> value.type == "Deleted"); 

You should check API for these questions.

You can use remove methods.

a.remove(1); 

OR

a.remove("acbd"); 

This will give you the output,

 ArrayList<String> l= new ArrayList<String>(); String[] str={"16","b","c","d","e","16","f","g","16","b"}; ArrayList<String> tempList= new ArrayList<String>(); for(String s:str){ l.add(s); } ArrayList<String> duplicates= new ArrayList<String>(); for (String dupWord : l) { if (!tempList.contains(dupWord)) { tempList.add(dupWord); }else{ duplicates.add(dupWord); } } for(String check : duplicates){ if(tempList.contains(check)){ tempList.remove(check); } } System.out.println(tempList); 

output,

[c, d, e, f, g] 

Just use myList.remove(myObject).

It uses the equals method of the class. See (java.lang.Object)

BTW, if you have more complex things to do, you should check out the guava library that has dozen of utility to do that with predicates and so on.

Use a iterator to loop through list and then delete the required object.

 Iterator itr = a.iterator(); while(itr.hasNext()){ if(itr.next().equals("acbd")) itr.remove(); } 

use contains() method which is available in list interface to check the value exists in list or not.If it contains that element, get its index and remove it

Snippet to remove a element from any arraylist based on the matching condition is as follows:

List<String> nameList = new ArrayList<>(); nameList.add("Arafath"); nameList.add("Anjani"); nameList.add("Rakesh"); Iterator<String> myItr = nameList.iterator(); while (myItr.hasNext()) { String name = myItr.next(); System.out.println("Next name is: " + name); if (name.equalsIgnoreCase("rakesh")) { myItr.remove(); } } 

Try below code :

 public static void main(String[] args) throws Exception{ List<String> l = new ArrayList<String>(); l.add("abc"); l.add("xyz"); l.add("test"); l.add("test123"); System.out.println(l); List<String> dl = new ArrayList<String>(); for (int i = 0; i < l.size(); i++) { String a = l.get(i); System.out.println(a); if(a.equals("test")){ dl.add(a); } } l.removeAll(dl); System.out.println(l); } 

your output :

 [abc, xyz, test, test123] abc xyz test test123 [abc, xyz, test123]