ort java.util.Set; public class MapUse{ //main driver code public static void main(String[] args) { HashMap map = new HashMap<>(); //insert map.put("abc", 1); map.put("def", 2); map.put("abc1", 10); map.put("def1", 20);
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import java.util.HashMap;
import java.util.Set;
public class MapUse{
//main driver code
public static void main(String[] args) {
HashMap<String, Integer> map = new HashMap<>();
//insert
map.put("abc", 1);
map.put("def", 2);
map.put("abc1", 10);
map.put("def1", 20);
map.put("abc", 5); //updates abc from 1 to 5, every key is unique, no dupplicate keys
//check size
System.out.println("size "+ map.size());
//check Presence
if(map.containsKey("abc")){
System.out.println("has abc");
}
if(map.containsKey("abc1")){
System.out.println("has abc1");
}
//get Value
int v = 0;
if(map.containsKey("abc1")){ //checks whether the key is actually present
v = map.get("abc1"); //to protect from null pointer exception
}
System.out.println(v);
//remove
int s = map.remove("abc"); //removes the value and also returns the value
System.out.println(s);
//iterate
Set<String> keys = map.keySet();
//gives a set of all keys as a Set
for(String str: keys){
System.out.println(str);
}
}.
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