Java java.util.Map.containsKey() method is used to check a key exits or not in Map. Java Map containsKey Method returns true if this java map contains a mapping for the given key .
Syntax of Map containsKey() method
public boolean containsKey(Object key) {
}
Parameters – key key whose presence in this map is to be tested
Return Value – true if this map contains a mapping for the given key
Example 1 : Java Map containsKey method -Value present
In this example we will initialize TreeMap using put() method . Then We will check Map contains key or not using map.containskey() meethod . Because there vogue and welcomes keys are present in Map , so map containsKey() method will return true .
import java.util.Map;
import java.util.TreeMap;
public class MapcontainsKey {
public static void main(String[] args) {
Map<String,Integer> treeMap = new TreeMap<String,Integer>();
treeMap.put("java",1);
treeMap.put("vogue",2);
treeMap.put("welcomes",3);
treeMap.put("you",4);
System.out.println("is key 'vogue' present = "+treeMap.containsKey("vogue"));
System.out.println("is key 'welcomes' present = "+treeMap.containsKey("welcomes"));
}
}
Output:
is key 'vogue' present = true
is key 'welcomes' present = true
Example 2 : Java Map containsKey method – Key not present
Map containsKey() method will return false if key not presentin Map . In this example we will check java map contains given key , then map.containskey() method returns false .
import java.util.Map;
import java.util.TreeMap;
public class MapcontainsKey1 {
public static void main(String[] args) {
Map<String,Integer> treeMap = new TreeMap<String,Integer>();
treeMap.put("java",1);
treeMap.put("vogue",2);
treeMap.put("welcomes",3);
treeMap.put("you",4);
System.out.println("is key 'tutorial' present = "+treeMap.containsKey("tutorial"));
System.out.println("is key 'treemap' present = "+treeMap.containsKey("treemap"));
}
}
Output:
is key 'tutorial' present = false
is key 'treemap' present = false
Example 3 : Map.containsKey() method – Mapping String to Integer keys
In this example we will check java map contains key using map containsKey() method . Now we will initialize Map have mapping String to Integer keys . We will check for keys 1 and 9 . Because key 1 is present in Map , So map containskey method return true and For key 9 map containsKey method return false .
import java.util.Map;
import java.util.TreeMap;
public class MapcontainsKey2 {
public static void main(String[] args) {
Map<Integer,String> treeMap = new TreeMap<Integer,String>();
treeMap.put(1,"java");
treeMap.put(2, "vogue");
treeMap.put(3,"welcomes");
treeMap.put(4,"you");
System.out.println("is key '1' present = "+treeMap.containsKey(1));
System.out.println("is key '2' present = "+treeMap.containsKey(9));
}
}
Output:
is key '1' present = true
is key '2' present = false
In this example we have learned how to check java map contains key using map containsKey() method . You can learn more java TreeMap program for practice .