SCJP Ch10 Development and Deployment.doc

SCJP Study Notes: Chapter 10 DevelopmentChapter 10 Development1. Using the javac and java Commands1.1 Compiling with javacIn the exam, you need to understand classpath and d option javac options source files javac -help -classpath optionjavac -classpath com:. -g Foo.java Bar.java-d option (assume no package statement)MyClass.classcurrent directoryjavac -d classes source/MyClass.java tell the compiler to put the .class file to classes dir = d (destination)-d option with package statementcurrent directorypackage com.wickedlysmart;public class MyClass javac -d ./classes com/wickedlysmart/MyClass.java If com/wickedlysmart not exist, the -d option will build it. But if classes dir not exist = ERROR1.2 Launching Applications with java java options class argsjava -DmyProp=myValue MyClass x 1 Create a system property called myProp and set its value to myValue the value pair is retrieved in System.getProperties( )java -DcmdProp=cmdVal take 2 TestProps/ if the value contain spaceCommand Line ArgumentsLegal Declaration:static public void main(String args) public static void main(String. x) static public void main(String bang_a_gong)args0, args1, if access args1 without the actual arg = ArrayIndexOutofBound1.3 Searching for Other ClassesBoth java and javac use the same search algorithm1. the first place they look at the directory come standard with J2SE2. the second place is the directory defined by classpath3. classpath can be defined in OS env var or in command line in java and javac4. command line override the env vare.g. classpath /com/foo/acct:/com/fooo the search path is separated by “:”, “/” means root directoryo noted that subdirectory, e.g. /com will NOT be searchedo in windows, use “;” and “”o can use -cpe.g. -classpath /com/foo/acct:/com/foo:.“.” = search also the current directoryPackages and Searchingpackage com.foo;public class MyClass public void hi( ) import com.foo.MyClass;import com.foo.*;public class Anothervoid go( ) MyClass m1 = new MyClass( );/ alias namecom.foo.Myclass m2 = new com.foo.MyClass( );/ full nameRelative and Absolute Pathse.g. -cp dirB:dirB/dirCo dirB and dirB/dirC are relative paths (they dont start with a slash /).o when the current directory is dirA, dirB and dirC will be searched, but not dirAo when the current directory is root, since dirB is not a direct subdirectory of root, no directories will be searchedo when the current directory is dirB, no directory will be searchede.g. -cp /dirB:/dirA/dirB/dirCo current directory is dirA, root? dirB? both paths in the classpath are absolute, it doesnt matter what is the current directory, /dirB is invalid since it is not a direct subdir of root, the ans is ONLY dirC2. JAR Files* You dont need to know how to make JAR files for the examo jar command create META-INF directory and MANIFEST.MF file automaticallyo jar command wont place any of your files in META-INF/Finding a JAR file using a classpath is similar to finding a package file in a classpath. The difference is that when you specify a path for a JAR file, you must include the name of the JAR file at the end of the pathjavac -classpath ws/myApp.jar UseStuff.javajavac -classpath ws UseStuff.java put JAR files into the ext subdirectory, java and javac can find them3. Using Static Importso What import statements do are just they save typing and make code easier to reado static import can import classs static member, static object and static membero if import both Integer and Long class and refer to MAX_VALUE = ERRORBefore static import:System.out.println(Integer.MAX_VALU