- Use -d to change the destination of a class file when it's first generated by the javac command.
- The -d option can build package-dependent destination classes on-the-fly if the root package directory already exists.
- Use the -D option in conjunction with the java command when you want to set a system property.
- System properties consist of name=value pairs that must be appended directly behind the -D, for example, java -Dmyproperty=myvalue.
- Command-line arguments are always treated as Strings.
- The java command-line argument 1 is put into array element 0, argument 2 is put into element 1, and so on
- Both java and javac use the same algorithms to search for classes.
- Searching begins in the locations that contain the classes that come standard with J2SE.
- Users can define secondary search locations using classpaths.
- Default classpaths can be defined by using OS environment variables.
- A classpath can be declared at the command line, and it overrides the default classpath.
- A single classpath can define many different search locations.
- In Unix classpaths, forward slashes (/) are used to separate the directories that make up a path. In Windows, backslashes () are used. ✓ Two-Minute Drill 809 810 Chapter 10: Development
- In Unix, colons (:) are used to separate the paths within a classpath. In Windows, semicolons (;) are used.
- In a classpath, to specify the current directory as a search location, use a dot (.)
- In a classpath, once a class is found, searching stops, so the order of locations to search is important
- When a class is put into a package, its fully qualified name must be used.
- An import statement provides an alias to a class's fully qualified name.
- In order for a class to be located, its fully qualified name must have a tight relationship with the directory structure in which it resides.
- A classpath can contain both relative and absolute paths.
- An absolute path starts with a / or a .
- Only the final directory in a given path will be searched
- An entire directory tree structure can be archived in a single JAR file.
- JAR files can be searched by java and javac.
- When you include a JAR file in a classpath, you must include not only the directory in which the JAR file is located, but the name of the JAR file too.
- For testing purposes, you can put JAR files into .../jre/lib/ext, which is somewhere inside the Java directory tree on your machine
- You must start a static import statement like this: import static
- You can use static imports to create shortcuts for static members (static variables, constants, and methods) of any class.