How to retrieve parent object by filtering out from the child object in java stream

Question

Person is my root POJA and I have list of phone number of as my child object.

String firstName;

String lastName;

Long id;

List<String> phoneNumber = new ArrayList<>();

int age;


public Person(String firstName, String lastName, int age, Long id, List<String> phone) {
    super();
    this.firstName = firstName;
    this.lastName = lastName;
    this.age = age;
    this.id = id;
    this.phoneNumber = phone;
}

List<Person> personList = Arrays.asList(
    new Person("Abdul", "Razak", 27, 50L, Arrays.asList("100", "101", "102")),
    new Person("Udemy", "tut", 56, 60L, Arrays.asList("200", "201", "202")),
    new Person("Coursera", "tut", 78, 20L, Arrays.asList("300", "301", "302")),
    new Person("linked", "tut", 14, 10L, Arrays.asList("400", "401", "402")),
    new Person("facebook", "tut", 24, 5L, Arrays.asList("500", "501", "502")),
    new Person("covila", "tut", 34, 22L, Arrays.asList("600", "602", "604")),
    new Person("twitter", "tut", 64, 32L, Arrays.asList("700", "702", "704"))
);

List<String> list = personList.stream()
    .map(p -> p.getPhoneNumber().stream())
    .flatMap(inputStream -> inputStream)
    .filter(p -> p.contains("502"))
    .collect(Collectors.toList());

I would like to retrieve person whose numbers equals to specific string. Is it possible to achieve this by using stream ?.

List<String> list = personList.stream()
    .map(p -> p.getPhoneNumber().stream())
    .flatMap(inputStream -> inputStream)
    .filter(p -> p.contains("502"))
    .collect(Collectors.toList());

In simple, How to retrieve parent object by filtering child object ?

Naman · Accepted Answer · 2017-10-03 09:11:04Z

4

personList.stream().filter((person)->person.getContacts().contains("100"))
                .collect(Collectors.toList());

Will give you the matched Person.

edited Oct 3, 2017 at 9:11

Naman

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answered Oct 3, 2017 at 8:51

Mehraj Malik

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1 Comment

Abdul Razak AK Over a year ago

Thank you. Assessed too highly by using flatmap to get child object

Naman · Accepted Answer · 2017-10-03 08:43:32Z

2

I would like to retrieve person whose numbers equals to specific string

List<Person> list = personList.stream().filter(p -> p.getPhoneNumber().contains("502"))
                     .collect(Collectors.toList())

This shall get you the list of Person whose list of phoneNumbers consists of "502" as a string.

answered Oct 3, 2017 at 8:43

Naman

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Comments

hiren · Accepted Answer · 2017-10-03 09:08:15Z

1

Try this List<Person> collect = personList.stream().filter(person -> person.phoneNumber.contains("502")).collect(Collectors.toList());

answered Oct 3, 2017 at 9:08

hiren

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1 Comment

hiren Over a year ago

to get person phonenumber list... you can also get it by getter method or by calling . operator. Have you tried this code ? It is working fine.. please check before commenting

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