Get all variable names in a class

Field[] fields = YourClassName.class.getFields();

returns an array of all public variables of the class.

getFields() return the fields in the whole class-heirarcy. If you want to have the fields defined only in the class in question, and not its superclasses, use getDeclaredFields(), and filter the public ones with the following Modifier approach:

Modifier.isPublic(field.getModifiers());

The YourClassName.class literal actually represents an object of type java.lang.Class. Check its docs for more interesting reflection methods.

The Field class above is java.lang.reflect.Field. You may take a look at the whole java.lang.reflect package.

You can use any of the two based on your need:

Field[] fields = ClassName.class.getFields(); // returns inherited members but not private members.
Field[] fields = ClassName.class.getDeclaredFields(); // returns all members including private members but not inherited members.

To filter only the public fields from the above list (based on requirement) use below code:

List<Field> fieldList = Arrays.asList(fields).stream().filter(field -> Modifier.isPublic(field.getModifiers())).collect(
    Collectors.toList());