Question

Saw this code online an im trying to understand each step. Can someone add comments to this ?

package javaapplication5;

interface PairInterface<String>{
void setFirst(String first);
void setSecond(String second);
String getFirst();
String getSecond();
  
}
class BasicPair<String> implements PairInterface{
String first;
String second;
BasicPair(String first,String second){
this.first=first;
this.second=second;
}

@Override
public String getFirst() {
return first;
}

@Override
public String getSecond() {
return second;
}

@Override
public void setFirst(Object first ) {
this.first=(String)first;
}

@Override
public void setSecond(Object second) {
this.second=(String)second;
}

  

  
}
class ArrayPair<String> implements PairInterface{

  
String first;
String second;
ArrayPair(String first,String second){
this.first=first;
this.second=second;
}
@Override
public String getFirst() {
return first;
}

@Override
public String getSecond() {
return second;
}

@Override
public void setFirst(Object first ) {
this.first=(String)first;
}

@Override
public void setSecond(Object second) {
this.second=(String)second;
}
  
}
class DriverApplication {
  
public static void main(String args[]){
PairInterface<String> myPair =
new BasicPair<>("apple", "peach");
System.out.print(myPair.getFirst() + " ");

myPair.setSecond("orange");
System.out.println(myPair.getSecond());
  
ArrayPair[] array2=new ArrayPair[2];
array2[0]=new ArrayPair<String>("apple","peach");
System.out.print(array2[0].getFirst()+" ");
array2[0].setSecond("orange");
System.out.println(array2[0].getSecond());

}
}

Answer 1

package javaapplication5;

interface PairInterface<String>{//basically this is an interface and it will not have any concrete methods as the name suggests as this is a pair here we have two getter methods and two setter methods
//setters used to set a value
void setFirst(String first);
void setSecond(String second);
//getters use to get the value
String getFirst();
String getSecond();
  
}
class BasicPair<String> implements PairInterface{//here with clas BasicPair we are implementing the abive interface, as we are implementing the interface we need to implement the methods in that interface
//defined two variables
String first;
String second;
//coonstructor to initialize thw variables
BasicPair(String first,String second){
this.first=first;
this.second=second;
}
//as we said we need to implement the methods in above interface we are overriding the methods @override annotation indicating the same
@Override
public String getFirst() {
return first;
}
//as we said we need to implement the methods in above interface we are overriding the methods @override annotation indicating the same
@Override
public String getSecond() {
return second;
}
//as we said we need to implement the methods in above interface we are overriding the methods @override annotation indicating the same
@Override
public void setFirst(Object first ) {
this.first=(String)first;
}
//as we said we need to implement the methods in above interface we are overriding the methods @override annotation indicating the same
@Override
public void setSecond(Object second) {
this.second=(String)second;
}

  

  
}
class ArrayPair<String> implements PairInterface{//here with clas ArrayPair we are implementing the abive interface, as we are implementing the interface we need to implement the methods in that interface

//to variables
String first;
String second;
//constructor to initialize thw variables
ArrayPair(String first,String second){
this.first=first;
this.second=second;
}
//as we said we need to implement the methods in above interface we are overriding the methods @override annotation indicating the same
@Override
public String getFirst() {
return first;
}
//as we said we need to implement the methods in above interface we are overriding the methods @override annotation indicating the same
@Override
public String getSecond() {
return second;
}
//as we said we need to implement the methods in above interface we are overriding the methods @override annotation indicating the same
@Override
public void setFirst(Object first ) {
this.first=(String)first;
}
//as we said we need to implement the methods in above interface we are overriding the methods @override annotation indicating the same
@Override
public void setSecond(Object second) {
this.second=(String)second;
}
  
}
//this a class with main method used to test the above classes
class DriverApplication {
  
public static void main(String args[]){
//here cretaed the objects for the above two class and printe dthose object svalues
PairInterface<String> myPair =
new BasicPair<>("apple", "peach");
System.out.print(myPair.getFirst() + " ");

myPair.setSecond("orange");
System.out.println(myPair.getSecond());
  
ArrayPair[] array2=new ArrayPair[2];
array2[0]=new ArrayPair<String>("apple","peach");
System.out.print(array2[0].getFirst()+" ");
array2[0].setSecond("orange");
System.out.println(array2[0].getSecond());

}
}