Filter method of the Stream class

Filter using List

package com.demo.java8;

import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;

public class Demo {
	public static void main(String[] args) {
		List<Emp> empList = Arrays.asList(new Emp[] { 
				new Emp("1","Mumbai","20"),
				new Emp("2","Delhi","23"),
				new Emp("3","Kolkata","25"),
				new Emp("4","Chennai","18"),
				new Emp("5","Mumbai","11"),
				new Emp("6","Kolkata","30"),
				new Emp("7","Chennai","35"),
				new Emp("8","Mumbai","15"),
				new Emp("9","Delhi","22"),
				new Emp("10","Kolkata","27")
				});
		
		//Example 1
		//Filter people of City Mumbai
		List<Emp> filteredList1 = empList.stream()
				.filter(x->x.getCity().equalsIgnoreCase("mumbai"))
				.collect(Collectors.toList());
		
		//Example 2		
		//Filter people of City Delhi who has age greater than 18 
		List<Emp> filteredList2 = empList.stream()
				.filter(x->x.getCity().equalsIgnoreCase("delhi"))
				.filter(x->Integer.parseInt(x.getAge())>18)
				.collect(Collectors.toList());
		
		//Example 3
		//Filter people of Delhi and kolkata who has if greater than 5
		empList.stream()
		.filter(x->(x.getCity().equalsIgnoreCase("delhi") || x.getCity().equalsIgnoreCase("kolkata")))
		.filter(x->Integer.parseInt(x.getId()) > 5)
		.forEach(System.out::println);
		
		System.out.println(filteredList1);
		System.out.println(filteredList2);
	}
}
class Emp{
	private String id;
	private String city;
	private String age;
	public Emp(String id, String city, String age) {
		super();
		this.id = id;
		this.city = city;
		this.age = age;
	}
	public String getId() {return id;}
	public String getCity() {return city;}
	public String getAge() {return age;}
	@Override
	public String toString() {
		return "Emp [id=" + id + ", city=" + city + ", age=" + age + "]";
	}
}

Filter using map

Example :

package com.demo.java8;

import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;

public class Demo2 {
	public static void main(String[] args) {
		Map<Integer,String> monthMap = new HashMap<>();
		monthMap.put(1,"JAN");
		monthMap.put(2,"FEB");
		monthMap.put(3,"MAR");
		monthMap.put(4,"APR");
		monthMap.put(5,"MAY");
		monthMap.put(6,"JUN");
		monthMap.put(7,"JUL");
		monthMap.put(8,"AUG");
		monthMap.put(9,"SEP");
		monthMap.put(10,"OCT");
		monthMap.put(11,"NOV");
		monthMap.put(12,"DEC");
		
		Map<Integer,String> filterMap = monthMap
											.entrySet()
											.stream()
											.filter(x->x.getKey() >5)
//											.collect(Collectors.toMap(x->x.getKey(), x->x.getValue())); //valid way but not recommended
											.collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue)); //Recommended way
		
		List<String> months = monthMap.entrySet().stream()
												.map(x->x.getValue())
												.collect(Collectors.toList());
		
	}
}