Использование сканера:
import java.util.*;
public class Swap {
public static void main(String[] args){
int i,temp,Num1,Num2;
Scanner sc=new Scanner(System.in);
System.out.println("Enter Number1 and Number2");
Num1=sc.nextInt();
Num2=sc.nextInt();
System.out.println("Before Swapping Num1="+Num1+" Num2="+Num2);
temp=Num1;
Num1=Num2;
Num2=temp;
System.out.println("After Swapping Num1="+Num1+" Num2="+Num2);
}
}