Hi I have an arraylist of arraylist in this format:
[[val1, val2],[val3,val4],[val1,val2],[val1,val5]]
and would like to get the unique set of arraylists:
[[val1, val2],[val3,val4],[val1,val5]]
I have tried the following:
Set<String> uniques = new HashSet<>();
for (ArrayList<String> sublist : mappedEntities) {
uniques.addAll(sublist);
}
but this merges all the values of the internal arraylist together
can use Java 8 Collection Stream Distinct,
return in Set datatype :
Set<List<String>> uniques = mappedEntities.stream().distinct().collect(Collectors.toSet());
if you want return in List :
List<List<String>> uniques = mappedEntities.stream().distinct().collect(Collectors.toList());
Why not simply put them in a Set like this?
Set<List<String>> uniques = new HashSet<>(mappedEntities);
Your mistake is that you are flattening the inner lists and putting their items in the set separately.
The issue here is that you need a Set of ArrayList Set<ArrayList<String>>, but you are using a Set of Strings Set<String> instead.
Given the list :
List<List<String>> mappedEntities = Arrays.asList(Arrays.asList("val1", "val2"),
Arrays.asList("val3", "val4"),
Arrays.asList("val1", "val2"),
Arrays.asList("val1", "val5"));
All you need to do is just declare the set and use the addAll().
Set<List<String>> mySet = new HashSet<>();
mySet.addAll(mappedEntities);
Since a set can hold only unique values, all duplicates will not be added to the set (No need to explicitly check this). You can now print it out :
mySet.forEach(System.out::println);
Or more simply, initialize the HashSet using the list mappedEntities :
Set<List<String>> mySet = new HashSet<>(mappedEntities);
I am beginner on STACKOVERFLOW but i to try solve your problem
I think you want like this..
import java.util.*;
public class GFG {
public static void main(String[] args)
{
int n = 3;
// Here aList is an ArrayList of ArrayLists
ArrayList<ArrayList<String> > aList =
new ArrayList<ArrayList<String> >(n);
// Create n lists one by one and append to the
// master list (ArrayList of ArrayList)
ArrayList<String> a1 = new ArrayList<String>();
a1.add("1");
a1.add("2");
aList.add(a1);
ArrayList<String> a2 = new ArrayList<String>();
a2.add("11");
a2.add("22");
aList.add(a2);
ArrayList<String> a3 = new ArrayList<String>();
a3.add("1");
a3.add("2");
aList.add(a3);
Set<ArrayList<String>> uniques = new HashSet<ArrayList<String>>();
for (ArrayList<String> sublist : aList) {
uniques.add(sublist);
}
System.out.println("Your Answer");
for (ArrayList<String> x : uniques)
System.out.println(x);
}
}
try this code:
public class B {
public static void main(String[] args) throws Exception {
List<List<String>> list= Arrays.asList(
Arrays.asList("a","b","c"),
Arrays.asList("a","b","c"),
Arrays.asList("a","b","c","d"));
Set<List<String>> uniques = new HashSet<>();
for (List<String> sublist : list) {
if(!uniques.contains(sublist))
uniques.add(sublist);
}
System.out.println(uniques);
}
}
output:
[[a, b, c], [a, b, c, d]]
Related
I want to merge two corresponding values of two different variables with comma separator in a row :
like
Plate Numbers(Output) : MH 35353, AP 35989, NA 24455, DL 95405.
There is two different variables one is plate State and another is plate Number, I want to merge them together with their corresponding values like 1st values of plate State with 1st value of plate Number after that comma then so on..
I tried this code snippet but didn't work :
ArrayList<String>
list1 = new ArrayList<String>();
list1.add("MH");
list1.add("AP");
list1.add("NA ");
list1.add("DL");
ArrayList<String>
list2 = new ArrayList<String>();
list2.add("35353");
list2.add("35989");
list2.add("24455");
list2.add("95405");
list1.addAll(list2);
use this :
ArrayList<String>
list1 = new ArrayList<String>();
list1.add("MH");
list1.add("AP");
list1.add("NA ");
list1.add("DL");
ArrayList<String>
list2 = new ArrayList<String>();
list2.add("35353");
list2.add("35989");
list2.add("24455");
list2.add("95405");
Iterator iterable = list2.iterator();
List<String> list3 =list1.stream()
.map(x->{
x= x+" "+((String) iterable.next());
return x;})
.collect(Collectors.toList());
String output = String.join(", ", list3);
System.out.println(output);
From ArrayList#addAll Javadoc:
Appends all of the elements in the specified collection to the end of this list[...]
This is not what you want, because you actually don't want to append the objects, you want to merge the String of the first list with the String from the second list. So in a sense, not merge the List but merge the objects (Strings) in the lists.
The easiest (most beginner friendly) solution would be to just create a simple helper method yourself, that does what you need.
Something like this:
public static void main(String[] args) {
ArrayList<String> list1 = new ArrayList<String>();
list1.add("MH");
list1.add("AP");
list1.add("NA");
list1.add("DL");
ArrayList<String> list2 = new ArrayList<String>();
list2.add("35353");
list2.add("35989");
list2.add("24455");
list2.add("95405");
ArrayList<String> combined = combinePlateNumbers(list1, list2);
System.out.println(combined);
}
private static ArrayList<String> combinePlateNumbers(List<String> list1, List<String> list2) {
ArrayList<String> result = new ArrayList<>();
if (list1.size() != list2.size()) {
// lists don't have equal size, not compatible
// your decision on how to handle this
return result;
}
// iterate the list and combine the strings (added optional whitespace here)
for (int i = 0; i < list1.size(); i++) {
result.add(list1.get(i).concat(" ").concat(list2.get(i)));
}
return result;
}
Output:
[MH 35353, AP 35989, NA 24455, DL 95405]
Below is the program which has hashmap and adding list as keys. However duplicate list are being added. Now i want to remove all the duplicate list inside residing as values.
import java.util.*;
public class Test {
public static void main(String args[]) {
Map<String, List<Integer>> sample = new HashMap<String, List<Integer>>();
List first = new ArrayList();
first.add(1);
first.add(2);
first.add(3);
List second = new ArrayList();
second.add(4);
second.add(5);
second.add(6);
List third = new ArrayList();
third.add(1);
third.add(2);
third.add(3);
sample.put("first", first);
sample.put("second", second);
sample.put("third", third);
System.out.print(sample.size()); // Prints 3
// Need to Remove the duplicate lists
// Expects two keys with list first and second since third is duplicate value
// 1,23 and 4,5,6 instead of 1,2,3 4,5,6 and 1,2,3
}
}
May be this piece of code will work for you -
public static void main(String[] args) {
Map<String, List<Integer>> sample = new HashMap<String, List<Integer>>();
List first = new ArrayList();
first.add(1);
first.add(2);
first.add(3);
List second = new ArrayList();
second.add(4);
second.add(5);
second.add(6);
List third = new ArrayList();
third.add(1);
third.add(2);
third.add(3);
sample.put("first", first);
sample.put("second", second);
sample.put("third", third);
removeDuplicates(sample);
System.out.print(sample.size()); // now it will print 2
}
private static void removeDuplicates(Map<String, List<Integer>> sample) {
Collection<List<Integer>> list = sample.values();
for(Iterator<List<Integer>> itr = list.iterator(); itr.hasNext();) {
if(Collections.frequency(list, itr.next())>1) {
itr.remove();
}
}
}
This remove duplicate method will remove the duplicate values from the List.
How I can group all lists in list which contains same exact value.
List<List<String>> list = new ArrayList<>();
This list contains list1 list2 list3 and etc....
I want to find if list1.get(0) is the same as list2.get(0) if no check with list3.get(0) and etc...
Later I need to group lists if I find the same values in each.
For example if true add list1 and list3 and others which were found to
List<List<String>> list2 = new ArrayList<>();
Now check with list2.get(0) if equal to others if yes group them and add them to anoter:
List<List<String>> list3 = new ArrayList<>();
What I achieved so far:
private static void findEqualLists(List<List<String>> list) {
int i = 0;
for (List<String> list1 : list) {
if (!Collections.disjoint(list1, list.get(i))) {
System.out.println(list1.get(0)+list.get(i).get(0));
}else{
System.out.println(list1.get(0)+list.get(i).get(0));
}
i++;
}
}
Value exmaple:
list = {{2017-02,jhon,car},{2017-03,maria,car},{2017-03, boy, car}, {2017-01,arya, car}, {2017-02, girl, car}}
Output:
Group1:
2017-03,maria,car
2017-03, boy, car
Group2:
2017-02,jhon,car
2017-02, girl, car
Group3
2017-01,arya, car
You want Collectors.groupingBy:
private static Map<String, List<List<String>>>
findEqualLists(List<List<String>> list) {
return list.stream().collect(Collectors.groupingBy(l -> l.get(0)));
}
The returned Map will use l.get(0) as a unique key, with each corresponding value being a List of only those Lists whose first element matches that key.
Now I can get list A, list B. And I want to get a new list which is A-(intersection of A and B). But when I get the intersection, it is [].
List<Map<String,String>> userDevices = clientdeviceService.getUserDevice(userId);
List<String> selectedDevices = new ArrayList<String>(Arrays.asList(devices));//selectedDevices is------[stress0012,stress0014,]
List<String> originalDevices = new ArrayList<String>();
List<String> originalDevicesRetain = new ArrayList<String>();//copy for operating
for(Map<String,String> originalDevId : userDevices){
originalDevices.add(originalDevId.get("DEVID"));
}
originalDevicesRetain.addAll(originalDevices);
originalDevicesRetain.retainAll(selectedDevices);
//originalDevicesRetain now is [],and it return false.
originalDevices.removeAll(originalDevicesRetain);
if(!originalDevices.isEmpty()){
}
Why originalDevices is [] has no elements in it?
I made this Code:
Class class{
public void main(String args[]){
ArrayList<ArrayList>list = new ArrayList<>();
ArrayList<String> Stringlist1 = new ArrayList<>();
ArrayList<String> Stringlist2 = new ArrayList<>();
Stringlist1.add("A");
Stringlist1.add("C");
Stringlist1.add("B");
Stringlist2.add("tr");
Stringlist2.add("rgd");
Stringlist2.add("sg");
}}
and i want to get the items from the inner list like:
for(ArrayList<String> ArrList: list){
ArrList.get(0)
}
pleas tell me how to do this!
ArrayList<ArrayList<String>> list = new ArrayList<>();
ArrayList<String> stringlist1 = new ArrayList<>();
ArrayList<String> stringlist2 = new ArrayList<>();
list.add(stringlist1);
list.add(stringlist2);
stringlist1.add("A");
stringlist1.add("C");
stringlist1.add("B");
stringlist2.add("tr");
stringlist2.add("rgd");
stringlist2.add("sg");
for(ArrayList<String> arrList: list){
for (String str : arrList) {
// do something
}
}
You can try something like this:
ArrayList<ArrayList<String>>list = new ArrayList<>();
//add items to StringLists
list.add(Stringlist1);
list.add(Stringlist2);
//Now access elements in your for loop
ArrayList<ArrayList<String>> list = new ArrayList<>();
ArrayList<String> stringlist1 = new ArrayList<>();
ArrayList<String> stringlist2 = new ArrayList<>();
stringlist1.add("A");
stringlist1.add("B");
stringlist1.add("C");
stringlist2.add("tr");
stringlist2.add("rgb");
stringlist2.add("sg");
list.add(stringlist1);
list.add(stringlist2);
//loop
System.out.println(list.get(0).get(0));
A nested for loop or for each loop is required.
You first need to add the sub lists to your parent list or you are not going to have access to the sub lists. Other than that, your code is mostly correct, except for not looping through each sub list.
The below code does exactly what you need so just copy it into your main function and it will work.
// create top level list
ArrayList<ArrayList<String>> list = new ArrayList<>();
// create sub lists
ArrayList<String> stringlist1 = new ArrayList<>();
ArrayList<String> stringlist2 = new ArrayList<>();
// add both sub lists to the parent list
list.add(stringlist1);
list.add(stringlist2);
// add elements to both lists
stringlist1.add("A");
stringlist1.add("C");
stringlist1.add("B");
stringlist2.add("tr");
stringlist2.add("rgd");
stringlist2.add("sg");
// loop through the top level list (will loop twice since the 2 elements are the sub lists)
for(ArrayList<String> array: list) {
System.out.println(array);
// loop through each element of each sub list
for (String str : array)
System.out.println(str);
}
Output:
[A, C, B]
A
C
B
[tr, rgd, sg]
tr
rgd
sg