Java 8 Stream Filter examples
Java 8 Stream API is very useful for filtering collections. Lets see example of java 8 filter API
class TempStudent {
public String name;
public int age;
public Address address;
public List<MobileNumber> mobileNumbers;
public TempStudent(String name, int age, Address address, List<MobileNumber> mobileNumbers) {
this.name = name;
this.age = age;
this.address = address;
this.mobileNumbers = mobileNumbers;
}
}
class Student{
private String name;
private int age;
private Address address;
private List<MobileNumber> mobileNumbers;
public Student(String name, int age, Address address, List<MobileNumber> mobileNumbers) {
this.name = name;
this.age = age;
this.address = address;
this.mobileNumbers = mobileNumbers;
}
public String getName() {
return name;
}
public int getAge() {
return age;
}
public Address getAddress() {
return address;
}
public List<MobileNumber> getMobileNumbers() {
return mobileNumbers;
}
public void setName(String name) {
this.name = name;
}
public void setAge(int age) {
this.age = age;
}
public void setAddress(Address address) {
this.address = address;
}
public void setMobileNumbers(List<MobileNumber> mobileNumbers) {
this.mobileNumbers = mobileNumbers;
}
@Override
public String toString() {
return "Student{" +
"name='" + name + '\'' +
", age=" + age +
", address=" + address +
", mobileNumbers=" + mobileNumbers +
'}';
}
}
class Address{
private String zipcode;
public Address(String zipcode) {
this.zipcode = zipcode;
}
public String getZipcode() {
return zipcode;
}
public void setZipcode(String zipcode) {
this.zipcode = zipcode;
}
}
class MobileNumber{
private String number;
public MobileNumber(String number) {
this.number = number;
}
public String getNumber() {
return number;
}
public void setNumber(String number) {
this.number = number;
}
}
Scenario
package com.javabypatel;
import java.util.Arrays;
import java.util.Comparator;
import java.util.List;
import java.util.Objects;
import java.util.Optional;
import java.util.stream.Collectors;
import java.util.stream.Stream;
public class StreamTest {
public static void main(String[] args) {
Student student1 = new Student(
"Jayesh",
20,
new Address("1234"),
Arrays.asList(new MobileNumber("1233"), new MobileNumber("1234")));
Student student2 = new Student(
"Khyati",
20,
new Address("1235"),
Arrays.asList(new MobileNumber("1111"), new MobileNumber("3333"), new MobileNumber("1233")));
Student student3 = new Student(
"Jason",
20,
new Address("1236"),
Arrays.asList(new MobileNumber("3333"), new MobileNumber("4444")));
List<Student> students = Arrays.asList(student1, student2, student3);
/*****************************************************
Get student with exact match name "jayesh"
*****************************************************/
Optional<Student> stud = students.stream()
.filter(student -> student.getName().equals("Jayesh"))
.findFirst();
System.out.println(stud.isPresent() ? stud.get().getName() : "No student found");
System.out.println("--------------------");
/*****************************************************
Get student with matching address "1235"
*****************************************************/
Optional<Student> stud1 = students.stream()
.filter(student -> student.getAddress().getZipcode().equals("1235"))
.findFirst();
System.out.println(stud1.isPresent() ? stud1.get().getName() : "No student found");
System.out.println("--------------------");
/*****************************************************
Get all student having mobile numbers 3333.
*****************************************************/
List<Student> stud2 = students.stream()
.filter(student111 -> student111.getMobileNumbers().stream().anyMatch(x -> Objects.equals(x.getNumber(), "3333")))
.collect(Collectors.toList());
String result1 = stud2.stream().map(std -> std.getName()).collect(Collectors.joining(",", "[", "]"));
System.out.println(result1);
System.out.println("--------------------");
/*****************************************************
Get all student having mobile number 1233 and 1234
*****************************************************/
List<Student> stud3 = students.stream()
.filter(student -> student.getMobileNumbers().stream().allMatch(x -> Objects.equals(x.getNumber(), "1233") || Objects.equals(x.getNumber(), "1234")))
.collect(Collectors.toList());
String result4 = stud3.stream().map(std -> std.getName()).collect(Collectors.joining(",", "[", "]"));
System.out.println(result4);
System.out.println("--------------------");
/*****************************************************
Create a List<Student> from the List<TempStudent>
*****************************************************/
TempStudent tmpStud1 = new TempStudent(
"Jayesh1",
201,
new Address("12341"),
Arrays.asList(new MobileNumber("12331"), new MobileNumber("12341")));
TempStudent tmpStud2 = new TempStudent(
"Khyati1",
202,
new Address("12351"),
Arrays.asList(new MobileNumber("11111"), new MobileNumber("33331"), new MobileNumber("12331")));
List<TempStudent> tmpStudents = Arrays.asList(tmpStud1, tmpStud2);
List<Student> studentList = tmpStudents.stream()
.map(tmpStud -> new Student(tmpStud.name, tmpStud.age, tmpStud.address, tmpStud.mobileNumbers))
.collect(Collectors.toList());
System.out.println(studentList);
System.out.println("--------------------");
/*****************************************************
Convert List<Student> to List<String> of student name
*****************************************************/
List<String> studentsName = studentList.stream()
.map(Student::getName)
.collect(Collectors.toList());
System.out.println(studentsName.stream().collect(Collectors.joining(",")));
System.out.println(studentsName.stream().collect(Collectors.joining(",", "[", "]")));
System.out.println("--------------------");
/*****************************************************
Convert List<students> to String
*****************************************************/
String name = students.stream()
.map(Student::getName)
.collect(Collectors.joining(",", "[", "]"));
System.out.println(name);
System.out.println("--------------------");
/*****************************************************
Change the case of List<String>
*****************************************************/
List<String> nameList =
Arrays.asList("Jayesh", "Dany", "Khyati", "Hello", "Mango");
nameList.stream()
.map(String::toUpperCase)
.forEach(System.out::println);
System.out.println("--------------------");
/*****************************************************
Sort List<String>
*****************************************************/
List<String> namesList =
Arrays.asList("Jayesh", "Dany", "Khyati", "Hello", "Mango");
namesList.stream()
.sorted()
.forEach(System.out::println);
System.out.println("--------------------");
/*****************************************************
Conditionally apply Filter condition, say if flag is enabled then
*****************************************************/
boolean sortConditionFlag = true;
Stream<Student> conditionalFilterResult = students.stream()
.filter(std -> std.getName().startsWith("J"));
if(sortConditionFlag){
conditionalFilterResult = conditionalFilterResult.sorted(Comparator.comparing(Student::getName));
}
System.out.println("Before sorting :");
students.forEach(s -> System.out.println(s.getName()));
List<Student> list = conditionalFilterResult.collect(Collectors.toList());
System.out.println("After filter and conditional sorting :");
list.forEach(s -> System.out.println(s.getName()));
}
}
OutputJayesh
--------------------
Khyati
--------------------
[Khyati,Jason]
--------------------
[Jayesh]
--------------------
[Student{name='Jayesh1', age=201, address=com.javabypatel.sea.Address@685cb137, mobileNumbers=[com.javabypatel.sea.MobileNumber@6a41eaa2, com.javabypatel.sea.MobileNumber@7cd62f43]},
Student{name='Khyati1', age=202, address=com.javabypatel.sea.Address@6d4b1c02, mobileNumbers=[com.javabypatel.sea.MobileNumber@6093dd95, com.javabypatel.sea.MobileNumber@5622fdf, com.javabypatel.sea.MobileNumber@4883b407]}]
--------------------
Jayesh1,Khyati1
[Jayesh1,Khyati1]
--------------------
[Jayesh,Khyati,Jason]
--------------------
JAYESH
DANY
KHYATI
HELLO
MANGO
--------------------
Dany
Hello
Jayesh
Khyati
Mango
--------------------
Before sorting :
Jayesh
Khyati
Jason
After filter and conditional sorting :
Jason
Jayesh
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Enjoy !!!!
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