Frequently Asked Questions

Note: I am putting these here because students have asked them in the past, this is not a reflection of what will be on quizzes. 

Q: How do you replace a char in a String?

A: This isn't as easy as it would be in something like an array. For a String first you will have to break apart the String using substring and then concatenate the pieces back together with the new letter. 

Q: How can I change char into int values?

A: With Casting. See the video here. 

Q: Can you change a char into a String or a String into a char?

A: Surprisingly it is easier to convert a char to an integer, see Casting, than it is to convert a String variable into a char. This is because Strings are Object types and not primitive types. You can however concatenate a char onto the end of a String or get the char at a specific index or location in a String.

Q: How do variables differ between programming languages? 

A: Many languages use the same types as Java just with different names, for example in SQL a String is a "varchar(225)" with the number representing how many letters there can be. In other languages you don't have to specify the type at all when you make a variable and the compiler or interpreter guesses what type of variable it is from what value it holds. 

Q: When are primitive data types like short and long used?

A: A long is used when the value that is being held has too many digits to fit into a normal integer. A phone number for example is too many digits to fit into a integer. Other variable types like float and short aren't used much any more, they were used when there wasn't enough space on computers but with modern computers we are less concerned with the space taken up by number values.  

Q: I'm still a little confused about what qualities distinguish a primitive variable type from object variable types.

A: A primitive type has only one attribute, one way of describing that thing. A char vs. a String is an example of this. A String has different values at different positions and a length while a char only has one value, you can't describe a character value past that single value but you can say several things about the String.

Q: Do all primitive variable types start with a lower case letter, and all objects start with an uppercase letter?

A: All primitive types do start with a lower case letter (e.g. int, char) and all Object types that are built into the language, like String, start with an upper case letter. You can however make your own object types and while it is good practice to create objects with upper case letters it is not required.