Hacks

import java.util.*;

public class Main {
    public static void main(String[] args) {

        //Scanner helps us to communicate with the machine and provide inputs.
        Scanner sc = new Scanner(System.in);

        System.out.println("Enter your first number");

        int a = sc.nextInt();

        System.out.println("Enter your second number");

        int b = sc.nextInt();

        Integer c = a + b;
        System.out.println("Binary Result: " + Integer.toBinaryString(c));
    }
}

Main.main(null);

Enter your first number
Enter your second number
Binary Result: 1101

import java.util.*;
class Yummy
{
public static void main(String arg[])	
{	
 
    Scanner sc=new Scanner(System.in);
    System.out.println("Enter a number");

    int n=sc.Integer();
    //Array that goes up to 100
    int  bin[]=new int[100];
//while n is greater than zero, we find the modulus repeatedly until n = 0
    int i = 0;
    while(n > 0)
    {
    bin[i++] = n%2;
       n = n/2;
    }
   System.out.print("Binary number: ");
    
    for(int j = i-1;j >= 0;j--)
   {
       System.out.print(bin[j]);
   }

   String output = Integer.toBinaryString(sum);

   System.out.println(firstentry + " + " + secondentry + " = " + output);
}
}

|       int n=sc.Integer();
cannot find symbol
  symbol:   method Integer()

|      String output = Integer.toBinaryString(sum);
cannot find symbol
  symbol:   variable sum

|      System.out.println(firstentry + " + " + secondentry + " = " + output);
cannot find symbol
  symbol:   variable firstentry

|      System.out.println(firstentry + " + " + secondentry + " = " + output);
cannot find symbol
  symbol:   variable secondentry

public class IntByReference {
    private int value;

    public IntByReference(Integer value) {
        this.value = value;
    }

    public String toString() {
        return (String.format("%d", this.value));
    }

    public void swapToLowHighOrder(IntByReference i) {
        if (this.value > i.value) {
            int tmp = this.value;
            this.value = i.value;
            i.value = tmp;
        }
    }

    public static void swapper(int n0, int n1) {
        IntByReference a = new IntByReference(n0);
        IntByReference b = new IntByReference(n1);
        System.out.println("Before: " + a + " " + b);
        a.swapToLowHighOrder(b);  // conditionally build swap method to change values of a, b
        System.out.println("After: " + a + " " + b);
        System.out.println();
    }

    public static void main(String[] ags) {
        IntByReference.swapper(21, 16);
        IntByReference.swapper(16, 21);
        IntByReference.swapper(16, -1);
    }

}
IntByReference.main(null);

Before: 21 16
After: 16 21

Before: 16 21
After: 16 21

Before: 16 -1
After: -1 16