Compare strings in two different arraylist (JAVA)

You can use the RemoveAll(Collection c) on one of the lists, if you happen to know if one list always contains them all.

You could use the following code:

    ArrayList<String> Alist = new ArrayList<String>();
    ArrayList<String> Blist = new ArrayList<String>();

    Alist.add("gsm");
    Alist.add("tablet");
    Alist.add("pc");
    Alist.add("mouse");

    Blist.add("gsm");
    Blist.add("something");
    Blist.add("pc");
    Blist.add("something");
    for (String a : Alist)
    {
        for (String b : Blist)
        {
            if (a.equals(b))
            {
                System.out.println("Equals " + a);
                break;
            }
        }
    }

Output is:
Equals gsm
Equals pc

right now your comparing each element to all of the other ones. Do something like

for (int i = 0; i < Alist.size(); i++) {
    if (!Alist.get(i).equals(Blist.get(i)) {
        // print what you want
    }
}

Thats of course assuming both lists have the same length.

Rather than writing code to manually compare list elements you might consider using Apache Commons Collections.

import org.apache.commons.collections.CollectionUtils;

List listA = ...;
List listB = ...;

Collection intersection = CollectionUtils.intersection(listA, listB);

import java.util.HashSet;

public class CheckSet<T> extends HashSet<T>{

    @Override
    public boolean add(T e) {
        if (contains(e)) {
            remove(e);
            return true;
        } else {
            return super.add(e);
        }
    }   
}

Add all elements of both of your lists to a CheckSet intance, and at the end it will only contain the ones not equal.

Here is one way:

    public static boolean compare(List<String> first, List<String> second) {
    if (first==null && second==null) return true;
    if (first!=null && second==null) return false;
    if (first==null && second!=null) return false;

    if ( first.size()!=second.size() ) return false;

    HashMap<String, String> map = new HashMap<String, String>();
    for (String str : first) {
        map.put(str, str);
    }
    for (String str : second) {
        if ( ! map.containsKey(str) ) {
            return false;
        }
    }
    return true;
}

import java.util.Arrays;
public class ExampleContains {
    public static boolean EligibleState(String state){
        String[] cities = new String[]{"Washington", "London", "Paris", "NewYork"};
        boolean test = Arrays.asList(cities).contains(state)?true:false;
        return test;
     }

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        System.out.println(EligibleState("London"));
    }

}