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Write a Java Program to Update value of HashMap using key
PROGRAM: Java Program to Update value of HashMap using key
/*Java Program to Update value of HashMap using key*/
1: Update value of HashMap using put()
import java.util.HashMap;
class Main {
public static void main(String[] args) {
HashMap<String, Integer> numbers = new HashMap<>();
numbers.put(“First”, 1);
numbers.put(“Second”, 2);
numbers.put(“Third”, 3);
System.out.println(“HashMap: ” + numbers);
// return the value of key Second
int value = numbers.get(“Second”);
// update the value
value = value * value;
// insert the updated value to the HashMap
numbers.put(“Second”, value);
System.out.println(“HashMap with updated value: ” + numbers);
}
}
2: Update value of HashMap using computeIfPresent()
import java.util.HashMap;
class Main {
public static void main(String[] args) {
HashMap<String, Integer> numbers = new HashMap<>();
numbers.put(“First”, 1);
numbers.put(“Second”, 2);
System.out.println(“HashMap: ” + numbers);
// update the value of Second
// Using computeIfPresent()
numbers.computeIfPresent(“Second”, (key, oldValue) -> oldValue * 2);
System.out.println(“HashMap with updated value: ” + numbers);
}
}
3: Update value of Hashmap using merge()
import java.util.HashMap;
class Main {
public static void main(String[] args) {
HashMap<String, Integer> numbers = new HashMap<>();
numbers.put(“First”, 1);
numbers.put(“Second”, 2);
System.out.println(“HashMap: ” + numbers);
// update the value of First
// Using the merge() method
numbers.merge(“First”, 4, (oldValue, newValue) -> oldValue + newValue);
System.out.println(“HashMap with updated value: ” + numbers);
}
}
