Java.util.TreeMap.put() and putAll() in Java
The insertion in TreeMap are handled using the variants of the put functions. There are two variants of put() in Java.util.TreeMap, both are discussed in this article.
1. put() : It associates the specified value with the specified key in the map. If a key is already present, then updating it results in updation of that key.
Parameters:
key : The key with which the value is to be associated.
value : The value to be associated with the given key.
Return Value:
It returns the previously associated value with this key,
or null if there was no mapping for key.
Exception:
Not Available.
import java.io.*;
import java.util.*;
public class Put {
public static void main(String[] args)
{
TreeMap<String, Integer> tmp = new TreeMap<String, Integer>();
tmp.put( "one" , 1 );
tmp.put( "two" , 3 );
System.out.println( "The initial TreeMap is : " + tmp);
int z = tmp.put( "two" , 2 );
System.out.println( "The previous value with two is : " + z);
System.out.println( "Updated TreeMap is : " + tmp);
}
}
|
Output:
The initial TreeMap is : {one=1, two=3}
The previous value with two is : 3
Updated TreeMap is : {one=1, two=2}
2. putAll() : It copies all of the mappings from the specified map to the given map and overwrites in case of repeated key.
Parameters:
map : The mappings to be stored.
Return Value:
Not Available.
Exception:
NullPointerException : Thrown if specified map is null,
specified map contains a null key.
import java.io.*;
import java.util.*;
public class putAll {
public static void main(String[] args)
{
TreeMap<String, Integer> tmp1 = new TreeMap<String, Integer>();
TreeMap<String, Integer> tmp2 = new TreeMap<String, Integer>();
tmp1.put( "two" , 3 );
tmp1.put( "one" , 1 );
tmp2.put( "three" , 3 );
tmp2.put( "two" , 2 );
System.out.println( "First treemap values are : " + tmp1);
tmp1.putAll(tmp2);
System.out.println( "Values after modifying 1st treemap : " + tmp1);
}
}
|
Output:
First treemap values are : {one=1, two=3}
Values after modifying 1st treemap : {one=1, three=3, two=2}
Exception
Null Pointer Exception : Occurs if the map contains a null key or it is null in putAll().
import java.io.*;
import java.util.*;
public class putAll {
public static void main(String[] args)
{
TreeMap<String, Integer> tmp1 = new TreeMap<String, Integer>();
TreeMap<String, Integer> tmp2 = new TreeMap<String, Integer>();
tmp1.put( "two" , 3 );
tmp1.put( "one" , 1 );
tmp2.put( "three" , 3 );
tmp2.put( null , 2 );
System.out.println( "First treemap values are : " + tmp1);
tmp1.putAll(tmp2);
System.out.println( "Values after modifying 1st treemap : " + tmp1);
}
}
|
Runtime Error :
Exception in thread "main" java.lang.NullPointerException
at java.util.TreeMap.put(TreeMap.java:563)
at putAll.main(putAll.java:21)
Practical Application : This function has the to store values and update them if we need. This kind of functionality is mainly useful in the directories and dictionaries or records. A small code below explains the combining databases to get updated score in a game.
import java.io.*;
import java.util.*;
public class putAllAppli {
public static void main(String[] args)
{
TreeMap<String, Integer> Score1 = new TreeMap<String, Integer>();
TreeMap<String, Integer> Score2 = new TreeMap<String, Integer>();
Score1.put( "Sachin" , 40 );
Score1.put( "Rahul" , 32 );
Score1.put( "Dhoni" , 68 );
System.out.println( "The scores till Drinks break are : " + Score1);
Score2.put( "Rahul" , 67 );
Score2.put( "Dhoni" , 102 );
Score2.put( "Raina" , 10 );
System.out.println( "The scores at Lunch : " + Score2);
Score1.putAll(Score2);
System.out.println( "Net scorecard is : " + Score1);
}
}
|
Output:
The scores till Drinks break are : {Dhoni=68, Rahul=32, Sachin=40}
The scores at Lunch : {Dhoni=102, Rahul=67, Raina=10}
Net scorecard is : {Dhoni=102, Rahul=67, Raina=10, Sachin=40}
Last Updated :
18 Sep, 2023
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