This simple Java program was created using the basics of object-oriented programming, such as objects, classes, etc.
The program contains 4 classes, each class performs a specific function
App.java : contains the Main method that call methods from other classes
input.java : contain 4 methods to convert from the base that user choose (FromBin,FromOct,FromDec,FromHex)
output.java : contain 4 methods to convert to other bases (ToBin,ToOct,ToDec,ToHex)
etc.java : contain side operations that used in other classes such as ERROR(); that shows an error message when it called