List<String> result = new ArrayList<String>();
        Set<String> set = new LinkedHashSet<String>();
        String s = "ravi is a good!boy. But ravi is very nasty fellow.";
        StringTokenizer st = new StringTokenizer(s, " ,. ,!");
        while (st.hasMoreTokens()) {
            result.add(st.nextToken());
        }
         System.out.println(result);
         set.addAll(result);
        result.clear();
        result.addAll(set);
        System.out.println(result);

output:
[ravi, is, a, good, boy, But, ravi, is, very, nasty, fellow]
[ravi, is, a, good, boy, But, very, nasty, fellow]

    ArrayList<String> list = new ArrayList<String>();
    HashSet<String> unique = new LinkedHashSet<String>();
    HashSet<String> dup = new LinkedHashSet<String>();
    boolean b = false;
    list.add("Hello");
    list.add("Hello");
    list.add("how");
    list.add("are");
    list.add("u");
    list.add("u");

    for(Iterator iterator= list.iterator();iterator.hasNext();)
    {
        String value = (String)iterator.next();
        System.out.println(value);

        if(b==unique.add(value))
            dup.add(value);
        else
            unique.add(value);


    }
    System.out.println(unique);
    System.out.println(dup);

for(int a=0;a<myArray.size();a++){
        for(int b=a+1;b<myArray.size();b++){
            if(myArray.get(a).equalsIgnoreCase(myArray.get(b))){
                myArray.remove(b); 
                dups++;
                b--;
            }
        }
}

用于自定义对象列表

   public List<Contact> removeDuplicates(List<Contact> list) {
    // Set set1 = new LinkedHashSet(list);
    Set set = new TreeSet(new Comparator() {

        @Override
        public int compare(Object o1, Object o2) {
            if (((Contact) o1).getId().equalsIgnoreCase(((Contact) o2).getId()) /*&&
                    ((Contact)o1).getName().equalsIgnoreCase(((Contact)o2).getName())*/) {
                return 0;
            }
            return 1;
        }
    });
    set.addAll(list);

    final List newList = new ArrayList(set);
    return newList;
}

public static void main(String[] args){
    ArrayList<Object> al = new ArrayList<Object>();
    al.add("abc");
    al.add('a');
    al.add('b');
    al.add('a');
    al.add("abc");
    al.add(10.3);
    al.add('c');
    al.add(10);
    al.add("abc");
    al.add(10);
    System.out.println("Before Duplicate Remove:"+al);
    for(int i=0;i<al.size();i++){
        for(int j=i+1;j<al.size();j++){
            if(al.get(i).equals(al.get(j))){
                al.remove(j);
                j--;
            }
        }
    }
    System.out.println("After Removing duplicate:"+al);
}

这样可以解决以下问题:

private List<SomeClass> clearListFromDuplicateFirstName(List<SomeClass> list1) {

     Map<String, SomeClass> cleanMap = new LinkedHashMap<String, SomeClass>();
     for (int i = 0; i < list1.size(); i++) {
         cleanMap.put(list1.get(i).getFirstName(), list1.get(i));
     }
     List<SomeClass> list = new ArrayList<SomeClass>(cleanMap.values());
     return list;
}