diff -r 02aabbf45b59 -r c3123d16bf3d java.rst --- a/java.rst Tue Feb 07 11:06:40 2012 +0200 +++ /dev/null Thu Jan 01 00:00:00 1970 +0000 @@ -1,129 +0,0 @@ --*- mode: outline; coding: utf-8; -*- - -* Class version. - -See value of 6 and 8 bytes in .class file: - - {0xCA, 0xFE, 0xBA, 0xBE, 0x00, minor, 0x00, major} - - major minor Java platform version - 45 0x27 3 1.0 - 45 0x27 3 1.1 - 46 0x28 0 1.2 - 47 0x29 0 1.3 - 48 0x30 0 1.4 - 49 0x31 0 1.5 - 50 0x32 0 1.6 - -* Modifiers. - -** public. - - * Public class is visible in other packages. - * Public field is visible everywhere (class must be public too). - -** private. - - * Private variables or methods may be used only by an instance of the same - class that declares the variable or method - * A private feature may only be accessed by the class that owns the feature. - -** protected. - - * Is available to all classes in the same package and also available to all - subclasses of the class that owns the protected feature. - * This access is provided even to subclasses that reside in a different - package from the class that owns the protected feature. - -** default. - -What you get by default ie, without any access modifier. - - * It means that it is visible to all within a particular package. - -* static. - - * Static means one per class, not one for each object no matter how many - instance of a class might exist. This means that you can use them without - creating an instance of a class. - * Static methods are implicitly final, because overriding is done based on - the type of the object, and static methods are attached to a class, not an - object. - * A static method in a superclass can be shadowed by another static method in - a subclass, as long as the original method was not declared final. - * You can't override a static method with a nonstatic method. - -* final. - - * A final class can't be extended ie., final class may not be subclassed. - * A final method can't be overridden when its class is inherited. - * You can't change value of a final variable. - -* Exceptions. - -A checked exception is some subclass of Exception (or Exception itself), -excluding class RuntimeException and its subclasses. - -Unchecked exceptions are RuntimeException and any of its subclasses. Class -Error and its subclasses also are unchecked. With an unchecked exception, -however, the compiler doesn't force client programmers either to catch the -exception or declare it in a throws clause. - -* Inner classes. - -** Nested top-level classes. - -If you declare a class within a class and specify the static modifier, the -compiler treats the class just like any other top-level class. - -Any class outside the declaring class accesses the nested class with the -declaring class name acting similarly to a package. eg, outer.inner. Top-level -inner classes implicitly have access only to static variables. There can also -be inner interfaces. All of these are of the nested top-level variety. - -** Member classes. - -Member inner classes are just like other member methods and member variables -and access to the member class is restricted, just like methods and variables. -This means a public member class acts similarly to a nested top-level class. - -The primary difference between member classes and nested top-level classes is -that member classes have access to the specific instance of the enclosing -class. - -** Local classes. - -Local classes are like local variables, specific to a block of code. Their -visibility is only within the block of their declaration. In order for the -class to be useful beyond the declaration block, it would need to implement a -more publicly available interface. - -Because local classes are not members, the modifiers public, protected, -private, and static are not usable. - -** Anonymous classes. - -Anonymous inner classes extend local inner classes one level further. As -anonymous classes have no name, you cannot provide a constructor. - -* 64-bit problem. - - http://www.java.com/en/download/faq/java_win64bit.xml - Which version of Java should I download for my 64-bit Windows - operating system? - http://java.sun.com/javase/6/webnotes/install/system-configurations.html - Java SE 6 Release Notes Supported System Configurations - -* Java performance. - - http://java.sun.com/performance/reference/whitepapers/5.0_performance.html - http://java.sun.com/performance/reference/whitepapers/6_performance.html - -* Creating jar. - - $ jar cf myFile.jar *.class - - $ jar cmf myManifestFile myFile.jar *.class - - $ jar -cfe Main.jar foo.Main foo/Main.class -