import java.util.Comparator;
public class Employee {
private String empName;
private String department;
private int age;
public Employee(String empName,String department,int age) {
this.empName = empName;
this.department = department;
this.age = age;
}
public static class OrderByName implements Comparator<Employee>
{
@Override
public int compare(Employee e1, Employee e2) {
// TODO Auto-generated method stub
return e1.empName.compareTo(e2.empName);
}
}
public static class OrderByDepartment implements Comparator<Employee>
{
@Override
public int compare(Employee e1, Employee e2) {
// TODO Auto-generated method stub
return e1.department.compareTo(e2.department);
}
}
public static class OrderByAge implements Comparator<Employee>
{
@Override
public int compare(Employee e1, Employee e2) {
// TODO Auto-generated method stub
return e1.age>e2.age?1:(e1.age<e2.age?-1:0);
}
}
/**
* @return the empName
*/
public String getEmpName() {
return empName;
}
/**
* @param empName the empName to set
*/
public void setEmpName(String empName) {
this.empName = empName;
}
/**
* @return the department
*/
public String getDepartment() {
return department;
}
/**
* @param department the department to set
*/
public void setDepartment(String department) {
this.department = department;
}
/**
* @return the age
*/
public int getAge() {
return age;
}
/**
* @param age the age to set
*/
public void setAge(int age) {
this.age = age;
}
}
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
public class Sample {
public static void main(String args[])
{
Employee e1 = new Employee("vaisakh","IT",21);
Employee e2 = new Employee("rajkumar","EEE",22);
Employee e3 = new Employee("binu","MECH",20);
List<Employee> list = new ArrayList<Employee>();
list.add(e1);
list.add(e2);
list.add(e3);
Collections.sort(list, new Employee.OrderByName());
System.out.println("Ordering based on name "+list);
Collections.sort(list, new Employee.OrderByDepartment());
System.out.println("Ordering based on department "+list);
Collections.sort(list, new Employee.OrderByAge());
System.out.println("Ordering based on age "+list);
}
}
public class Sample {
public static int findFibbonacci(int fibbNum)
{
if(fibbNum==1 || fibbNum==2)
{
return 1;
}
int f1=1;int f2=1;int fib=1;
for(int i=3;i<=fibbNum;i++)
{
fib=f1+f2;
f1=f2;
f2=fib;
}
return fib;
}
public static void main(String args[])
{
for(int i=1;i<10;i++)
{
System.out.println(findFibbonacci(i));
}
}
}
public class Sample {
public static String replaceChar(int index,String str,char replaceChar)
{
char[] charStr = str.toCharArray();
charStr[index] = replaceChar;
return String.valueOf(charStr);
}
public static void main(String args[])
{
System.out.println(replaceChar(6,"malayalam",'b'));
}
}public class HelloWorld{ static double pi = 3.14; static{System.out.println("static block is invoked");}
public static void main(String[] args) {
System.out.println("main block");
}
public class HelloWorld{ static double pi = 3.14;
static void calc(double a) {
pi = a;
System.out.println("Value pi is: "+a);
}
public static void main(String[] args) {
HelloWorld.calc(55.3);//accessing the static method
}
}
package com.jobberindia;package com.jobberindia;
import java.io.File;
import java.util.*;
public class HelloWorld {
void multiply(int a,int b)
{
int c = a*b;
System.out.println("After multiplication of"+a+" and "+b+"is: "+c);
}
void multiply(int a,double b)//one int and other double value
{
double c = a*b;
System.out.println("After multiplication of"+a+" and "+b+"is: "+c);
}
public static void main(String[] args) {
HelloWorld hw = new HelloWorld();
hw.multiply(5, 3);
hw.multiply(5, 6.6);
}
}
public static void main(String[] args) {
File file = new File("c:/filename.txt");
if(file.isHidden()){
System.out.println("The file is hidden");
}else{
System.out.println("The file is not hidden");
}
}
}
public class HelloWorld {
public static void main(String[] args) {
List<String> list = new ArrayList<String>();
list.add("Hello");
list.add("World");
list.add("Hello1");
list.add("World2");
Map<Integer,String> map = new HashMap<Ineger,String>();
for(int i=0;i<list.size();i++)
{
map.put(i, list.get(i));
}
System.out.println("Data stored in mainlist "+map.get(2));
}
}
package com.jobberindia;
import java.util.*;
public class HelloWorld {
public static void main(String[] args) {
Set<String> set = new TreeSet<String>();
set.add("Hello");
set.add("World");
set.add("Hello1");
set.add("World2");
set.add("Hello3");
set.add("World4");
System.out.println("Data stored in mainlist "+set);
}
}
package com.jobberindia;
import java.util.*;
public class HelloWorld {
public static void main(String[] args) {
// TODO Auto-generated method stub
List<String> list = new ArrayList<String>();
list.add("Hello");
list.add("World");
list.add("Hello1");
list.add("World2");
System.out.println("Data stored in mainlist "+list);
System.out.println("Size of list before removing "+list.size());
ArrayList<String> subList = new ArrayList<String>(list.subList(1, 2));
System.out.println("Data stored in sublist "+subList);
System.out.println("Size of list before removing "+subList.size());
}
}public interface List<E>extends Collection<E>.
UnsupportedOperationExceptionClassCastExceptionNullPointerException IllegalArgumentExceptionIndexOutOfBoundsException public interface Set<E>
Set in Java allows to store objects by storing them in each index. Other than Set Set doesn't allows Duplication of elements.To store an element in Set use the add() method.
Example:
package com.jobberindia;import java.util.*;public class HelloWorld {public static void main(String[] args) {Set<String> set = new TreeSet<String>();set.add("Hello");set.add("World");set.add("Hello1");set.add("World2");set.add("Hello3");set.add("World4");System.out.println("Data stored in mainlist "+set);}}Some Classes implementing List Interface are TreeSet,HashSet etc.
What is Map in Java?Other than List and Set Map is used to Store Key and Value Pair.The key is unique and values are duplicate allowed. Map implement the collection Interface. It allows only one null value which is stored in the zeroth index.These are the some of the classes implements the Map<K,V> Interface. HashMap, Hashtable, IdentityHashMap, LinkedHashMap.Example:
- List allows duplicate values.
- List allows any number of null values.
- Set doesn't allows duplicate values.
- Set allows one null value.
- Map allows one null key value.
- List maintains the insertion order.
- Set and Map doesn't maintain the insertion order.
- Map stores key and value pair.
Based on your usage select these interfaces carefully.
/** * author: JOBBERINDIA
/**
* author: JOBBERINDIA */package com.jobberindia;
import java.util.*;/** * @author user * */public class HelloWorld {
/** * @param args */ public static void main(String[] args) { // TODO Auto-generated method stub List<String> list = new ArrayList<String>(); list.add("Hello"); list.add("World"); System.out.println("Size of list before removing"+list.size()); list.remove("Hello"); System.out.println("Size of list "+list.size()); }
}
- list.add(arg0);
- list.add(arg0, arg1);
- list.addAll(arg0);
- list.addAll(arg0, arg1);
- list.clear();
- list.contains(arg0);
- list.containsAll(arg0);
- list.containsAll(arg0);
- list.equals(arg0);
- list.get(arg0);
- list.size();
- list.isEmpty();
- list.lastIndexOf(arg0);
- list.remove(arg0);
- list.removeAll(arg0);
- list.toArray();
- list.toString();
public final class Test {
static int i;
int j;
// start of static block
static {
i = 10;
System.out.println("static block called ");
}
// end of static block
public static void main(String args[]) {
// Although we don't have an object of Test, static block is
// called because i is being accessed in following statement.
System.out.println(Test.i);
}
}
Output:
static block called
Constructor called
