generic and file handling

package employee;
import java.util.*;
import java.io.*;
public class Employee <U,V> implements Comparable <Employee> {
    private U a;
    private V b;

    public Employee(U a, V b) {
        this.a = a;
        this.b = b;
    }

    public U getA() {
        return a;
    }

    public void setA(U a) {
        this.a = a;
    }

    public V getB() {
        return b;
    }

    public void setB(V b) {
        this.b = b;
    }


    public static void main(String[] args) {
       ArrayList <Employee> arr = new ArrayList<Employee>();
       arr.add (new Employee ("Ali",1));
       arr.add (new Employee ("Ahmad",2));
       arr.add (new Employee ("Xhmad",5));
       arr.add(new Employee (2,"Saim"));
       arr.add(new Employee (1,"Xaim"));
       arr.add(new Employee (9,"Gaim"));
       Collections.sort(arr);
       for(Employee x:arr)
        System.out.println(x.getA()+" "+x.getB());
    }

    @Override
    public int compareTo(Employee o) {
        String one="",two="";
        int a=0,b=0;
       if (o.getA() instanceof String && this.getA() instanceof String){
           one = (String) o.getA();
           two = (String) this.getA();
           return two.compareTo(one);
    }
      /* else
           if (o.getB() instanceof String && this.getB() instanceof String){
           one = (String) o.getB();
           two = (String) this.getB();
           return one.compareTo(two);
           }*/
     /*  else
               if (o.getA() instanceof String && this.getB() instanceof String){
           one = (String) o.getA();
           two = (String) this.getB();
           return one.compareTo(two);
               }*/
       if(o.getA() instanceof Integer && this.getA() instanceof Integer)
       {
           a=(int) o.getA();
           //System.out.println(this.getA());
           b=Integer.parseInt((String.valueOf(this.getA())));
           return b-a;
       }
       return 0;
    }

}




Upper to Lower, Lower to Upper
package st2;
public class St2 {

public static void main(String[] args) {

String s="HelLo woRld @ 2017";
int i;
char[]c=s.toCharArray();
char[] k=new char[100];
int a=c.length;
for(i=0;i<a;i++)
{
if(Character.isUpperCase(c[i]))
{
c[i]=Character.toLowerCase(c[i]);
}
else if(Character.isLowerCase(c[i]))
{
c[i]= Character.toUpperCase(c[i]);
}
}
for(i=0;i<a;i++)
{
System.out.print(c[i]);
}
}
}




import java.io.*;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.StringTokenizer;
/**
* Created by test on 3/14/2017.
*/
public class Main{
public static void main(String[] args) throws Exception {
File country = new File("out\\country.txt");
File capital = new File("out\\capital.txt");
File combine = new File("out\\combine.txt");
FileReader f1 = new FileReader(country);
BufferedReader bf1 = new BufferedReader(f1);
String str = new String();
ArrayList<String> list = new ArrayList<String>();
int i = 0;
while((str = bf1.readLine()) != null) {
list.add(str);
i++;
}
Collections.sort(list);
bf1.close();
f1.close();
FileWriter wcountry= new FileWriter(country);
BufferedWriter bwcountry = new BufferedWriter(wcountry);
for (String ss: list) {
bwcountry.write(ss + "\n");
}
bwcountry.close();
wcountry.close();
FileWriter w1 = new FileWriter(capital);
BufferedWriter bw1 = new BufferedWriter(w1);
String delimiter = " ";
String comb = new String();
for (int k = 0; k < i; k++) {
int j =0;
FileReader f2 = new FileReader(combine);
BufferedReader bf2 = new BufferedReader(f2);
while((comb = bf2.readLine()) != null) {
StringTokenizer st = new StringTokenizer(comb, delimiter);
String name = st.nextToken();
String name2 = null;
if(name.equals(list.get(k))) {
name2 = st.nextToken();
bw1.write(name2 + "\n");
}
j++;
}
bf2.close();
f2.close();
}
bw1.close();
w1.close();
}