Learn Java 8 streams with an example - Filter a Map by keys and values

In this section, we will learn how to filter a Map using the Stream filter() method.

Example 1: Filter Map by Keys

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

/*Filter Map by Keys*/
public class DriverClass {
    public static void main(String[] args) {
        Map<Integer, String> hMap = new HashMap<Integer, String>();
        hMap.put(123, "Jessie");
        hMap.put(234, "Alpha");
        hMap.put(345, "Beta");
        hMap.put(456, "Tesla");
        hMap.put(111, "Tera");

        Map<Integer, String> output = hMap.entrySet()
                .stream()
                .filter(map -> map.getKey().intValue() <= 254)
                .collect(Collectors.toMap(map -> 
                    map.getKey(), map -> map.getValue()));
        System.out.println("Output: " + output);
    }
}
Output: 



Example 2: Filter Map by Values

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

/*Filter Map by Values*/
public class DriverClass {
    public static void main(String[] args) {
        Map<Integer, String> hMap = new HashMap<Integer, String>();
        hMap.put(123, "Tera");
        hMap.put(234, "Alpha");
        hMap.put(345, "Beta");
        hMap.put(456, "Tesla");
        hMap.put(111, "Tera");

        Map<Integer, String> output = hMap.entrySet()
                .stream()
                .filter(map -> "Tera".equals(map.getValue()))
                .collect(Collectors.toMap(map -> 
                     map.getKey(), map -> map.getValue()));
        System.out.println("Output: " + output);
    }
}
Output: 



Example 3: Filter Map by both Keys and Values

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

/*Filter Map by both Keys and Values*/
public class DriverClass {
    public static void main(String[] args) {
        Map<Integer, String> hMap = new HashMap<Integer, String>();
        hMap.put(193, "Tera");
        hMap.put(234, "Alpha");
        hMap.put(345, "Beta");
        hMap.put(456, "Tesla");
        hMap.put(111, "Tera");

        Map<Integer, String> output = hMap.entrySet()
                .stream()
                .filter(map -> "Tera".equals(map.getValue()))
                .filter(map ->map.getKey().intValue() <= 150)
                .collect(Collectors.toMap(map -> 
                   map.getKey(), map -> map.getValue()));
        System.out.println("Output: " + output);
    }
}
Output: 



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