From the Java tutorial:
Access level modifiers determine whether other classes can use a particular field or invoke a particular method. There are two levels of access control:
public, or package-private (no explicit modifier).
protected, or package-private (no explicit modifier).
A class may be declared with the modifier
public, in which case that class is visible to all classes everywhere. If a class has no modifier (the default, also known as package-private), it is visible only within its own package.
At the member level, you can also use the
public modifier or no modifier (package-private) just as with top-level classes, and with the same meaning. For members, there are two additional access modifiers:
private modifier specifies that the member can only be accessed in its own class. The
protected modifier specifies that the member can only be accessed within its own package (as with package-private) and, in addition, by a subclass of its class in another package.
The following table shows the access to members permitted by each modifier.