Java question [guys help me solve this question.]

Question

Write a program to convert numbers. The user should be able to select from a menu option and enter the number to convert. The program must do the conversion and display output. After that, the program must ask if the user wants to perform another conversion without exiting
1. Decimal to Binary
2. Binary to Decimal

2. Write a program to sum the digits in an integer. (use % and / operators) e.g. 1234 = 10

Answer 1

Display menu
Input user's choice
If choice is one
Call decimal to binary function
else if choice is two
Call binary to decimal function
else
Display error message or exit

Decimal to binary function
Display prompt
Read decimal string
Verify the string characters are valid
If not
Display error message
Else
Convert string to integer (parseInt)
String initialized to empty
While integer is not zero
String becomes new digit (integer%2) as character plus old string
Integer becomes old integer without digit (integer/2)
If string is empty
Display zero
Else
Display string

Binary to decimal function
Display prompt
Read binary string
Verify the string characters are valid
If not
Display error message
Else
Zero decimal number
For each character in binary string
If character is one
Add one to decimal
Multiply decimal by two
Display decimal

Answer 2

Thanks but I ne need it in a Java solution