HashMap in java
HashMap is a collection of data in pair , like a ("key","value").
Put
import java.util.HashMap;
public class Main
{
public static void main(String[] args)
{
HashMap<String,Integer> names = new HashMap<String,Integer>();
names.put("jack",1);
names.put("steve",2);
names.put("stark",3);
System.out.print(names);
}
}
Output
{stark=3, steve=2, jack=1}
Get
import java.util.HashMap;
public class Main
{
public static void main(String[] args)
{
HashMap<String,Integer> names = new HashMap<String,Integer>();
names.put("jack",1);
names.put("steve",2);
names.put("stark",3);
System.out.print(names.get("steve"));
}
}
Output
2
Remove
import java.util.HashMap;
public class Main
{
public static void main(String[] args)
{
HashMap<String,Integer> names = new HashMap<String,Integer>();
names.put("jack",1);
names.put("steve",2);
names.put("stark",3);
names.remove("steve");
System.out.print(names);
}
}
Output
{stark=3, jack=1}
Clear
import java.util.HashMap;
public class Main
{
public static void main(String[] args)
{
HashMap<String,Integer> names = new HashMap<String,Integer>();
names.put("jack",1);
names.put("steve",2);
names.put("stark",3);
names.clear();
System.out.print(names);
}
}
Output
{}
Size
import java.util.HashMap;
public class Main
{
public static void main(String[] args)
{
HashMap<String,Integer> names = new HashMap<String,Integer>();
names.put("jack",1);
names.put("steve",2);
names.put("stark",3);
System.out.print(names.size());
}
}
Output
3
print each element:
Method-1
import java.util.HashMap;
public class Main
{
public static void main(String[] args)
{
HashMap<String,Integer> names = new HashMap<String,Integer>();
names.put("jack",1);
names.put("steve",2);
names.put("stark",3);
for(String i : names.keySet())
{
System.out.println(i);
}
}
}
Output
stark steve jack
Method-2
import java.util.HashMap;
public class Main
{
public static void main(String[] args)
{
HashMap<String,Integer> names = new HashMap<String,Integer>();
names.put("jack",1);
names.put("steve",2);
names.put("stark",3);
for(int i : names.values())
{
System.out.println(i);
}
}
}
Output
3 2 1
Method-3
import java.util.HashMap;
public class Main
{
public static void main(String[] args)
{
HashMap<String,Integer> names = new HashMap<String,Integer>();
names.put("jack",1);
names.put("steve",2);
names.put("stark",3);
for(String i : names.keySet())
{
System.out.println(i+" : "+names.get(i));
}
}
}
Output
stark : 3 steve : 2 jack : 1
Another Types:
Put
import java.util.HashMap;
public class Main
{
public static void main(String[] args)
{
HashMap<String,String> names = new HashMap<String,String>();
names.put("google","Larry Page");
names.put("apple","Steve Jobs");
names.put("spaceX","Elon Musk");
System.out.println(names);
}
}
Output
{apple=Steve Jobs, spaceX=Elon Musk, google=Larry Page}