java sort list of strings by string value entered by a user

Question

I am looking for a way in java to sort a list of strings based on user input in Java. for example, my list contains ["Pat Henderson", "Zach Harrington", "Pat Douglas", "Karen Walsh"] , if a user enters the first name "Pat" how would I be able to print out only the Pats in the list and same for surnames?

Answer 1

ArrayList<String> str = new ArrayList<String>();

for(int i = 0 ; i < str.size() ; i++) {
    if(str.get(i).contains("your_user_input")) {
        System.out.println(str.get(i));
    }
}

Answer 2

.filter() introduced in Java 8 would to the thing.

List<String> names = new ArrayList<>();
names.addAll(Arrays.asList("Pat Henderson", "Zach Harrington", "Pat Douglas", "Karen Walsh"));

String startsWith = "Pat";

List<String> filteredNames = names.stream()
        .filter(name -> name.startsWith(startsWith))
        .collect(Collectors.toList());

A little remark. Sorting is when you rearrange the position of the elements without removing any.

Answer 3

Supposing that each element of the list have a name and a last name separated by a whitespace or more, with Java 8 you could filter on the name or the last name in this way :

List<String> list = Arrays.asList("Pat Henderson", "Zach Harrington", "Pat Douglas", "Karen Walsh");
String nameOrLastNameToFilter = ...;
list.stream().filter(s -> Arrays.stream(s.split("\\s+"))
                                .anyMatch(n->n.equals(nameOrLastNameToFilter))
                    )
    .collect(toList());