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java treemap example

TreeMap:-TreeMap is a implemented class of map interface where elements store on the basis of key value pair and according to some sorting order of keys .

Example1:- TestMap.java
import java.util.*;
class TestMap
{
public static void main(String[]args)
{
Map<Object,Object> m=new TreeMap<Object,Object>();
m.put(101,"Sumit");
m.put(104,"Sunita");
m.put(102,"Suman");
m.put(107,"Sonu");
Set s=m.entrySet();
Iterator itr=s.iterator();
System.out.println("Key   :::::::::Value");
while(itr.hasNext())
{
Map.Entry me=(Map.Entry)itr.next();
System.out.println(me.getKey()+"    :::: "+me.getValue());
}
}
}
Output:-
Key :::::::::Value
101    :::: Sumit
102    :::: Suman
104    :::: Sunita
107    :::: Sonu
Example2:- TestMap.java
import java.util.*;
class TestMap
{
public static void main(String[]args)
{
Map<Object,Object> m=new TreeMap<Object,Object>();
m.put("A","Sumit");
m.put("C","Sunita");
m.put("K","Suman");
m.put("B","Sonu");
Set s=m.entrySet();
Iterator itr=s.iterator();
System.out.println("Key   :::::::::Value");
while(itr.hasNext())
{
Map.Entry me=(Map.Entry)itr.next();
System.out.println(me.getKey()+"    :::: "+me.getValue());
}
}
}
Output:-
Key :::::::::Value
A    :::: Sumit
B    :::: Sonu
C    :::: Sunita
K    :::: Suman
Example3:- TestMap.java
import java.util.*;
class TestMap
{
public static void main(String[]args)
{
Map<Object,Object> m=new TreeMap<Object,Object>();
m.put(null,"Sonu");
Set s=m.entrySet();
Iterator itr=s.iterator();
System.out.println("Key   :::::::::Value");
while(itr.hasNext())
{
Map.Entry me=(Map.Entry)itr.next();
System.out.println(me.getKey()+"    :::: "+me.getValue());
}
}
}
Output:- Exception in thread "main" java.lang.NullPointerException.
Example4:-TestMap.java
import java.util.*;
class TestMap
{
public static void main(String[]args)
{
Map<Object,Object> m=new TreeMap<Object,Object>();
m.put(101,null);
m.put(102,null);
Set s=m.entrySet();
Iterator itr=s.iterator();
System.out.println("Key   :::::::::Value");
while(itr.hasNext())
{
Map.Entry me=(Map.Entry)itr.next();
System.out.println(me.getKey()+"    :::: "+me.getValue());
}
}
}
Output:-
Key :::::::::Value
101    :::: null
102    :::: null
Example5:-TestMap.java
import java.util.*;
class TestMap
{
public static void main(String[]args)
{
Map<Object,Object> m=new TreeMap<Object,Object>();
m.put(101,"Sonu");
m.put(102,"Monu");
m.put(101,"Mona");
Set s=m.entrySet();
Iterator itr=s.iterator();
System.out.println("Key   :::::::::Value");
while(itr.hasNext())
{
Map.Entry me=(Map.Entry)itr.next();
System.out.println(me.getKey()+"    :::: "+me.getValue());
}
}
}
Output:-
Key :::::::::Value
101    :::: Mona
102    :::: Monu
Example6:-TestMap.java
import java.util.*;
class Student
{
int rollno;
String name,course;
Student(int rollno,String name,String course)
{
this.rollno=rollno;
this.name=name;
this.course=course;
}
}
class TestMap
{
public static void main(String[]args)
{
Map<Object,Student> m=new TreeMap<Object,Student>();
Student s1=new Student(101,"Neha","M.Tech");
Student s2=new Student(102,"Nisha","B.Tech");
Student s3=new Student(103,"Nehal","M.C.A");
Student s4=new Student(104,"Namita","MSC");
m.put(1033,s3);
m.put(1044,s4);
m.put(1011,s1);
m.put(1022,s2);
Set ss=m.entrySet();
Iterator itr=ss.iterator();
System.out.println("Key   :::::::::Value");
while(itr.hasNext())
{
Map.Entry me=(Map.Entry)itr.next();
Student s=(Student)me.getValue();
System.out.println(me.getKey()+"    :::: "+s.rollno+"  "+s.name+"  "+s.course);
}
}
}
Output:-
Key   :::::::::Value
1011    :::: 101  Neha  M.Tech
1022    :::: 102  Nisha  B.Tech
1033    :::: 103  Nehal  M.C.A

1044    :::: 104  Namita  MSC
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