Packages are used to group related classes and interfaces together. The
package keyword is used to group a class or interface into a package.
Java Common Packages
Packages in the Java language itself begin with the
javax.. The Java Platform classes are organized into packages, here are the some common packages :
This package provides the classes fundamental to the design of the Java programming language. The classes in this package are automatically available. There's no need to import them.
All primitive types are defined in this package. Here are some classes defined in the
java.lang package :
Boolean Byte Character Double Float Integer Long Math Number Object String Thread
The package provides for system input and output through data stream , serialization and the file system. Some classes in the package are :
BufferedInputStream BufferedOutputStream BufferedReader BufferedWriter Console File fileReader FileWriter InputStream InputStreamReader OutputStream OutputStreamWriter Reader StringReader Writer
Contains the collection framework, legacy collection classes, event model, date and time facilities, internationalization and miscellaneous utility classes(a string tokenizer, a random-number generator and a bit array).
Some classes and interfaces in the package are :
Collection<E> Comparator<T> List<E> Map<K,V> Queue<E> Set<E> Arrays ArrayList<E> Date Collections Dictionary<K,V> LinkedList<E> Scanner UUID
Contains classes and interfaces for handling text, dates, numbers, and messages in a manner independent of natural languages.
Some classes in the package are :
Annotation DateFormat DecimalFormat NumberFormat SimpleDateFormat