1 -*- mode: outline; coding: utf-8; -*- |
|
2 |
|
3 * Class version. |
|
4 |
|
5 See value of 6 and 8 bytes in .class file: |
|
6 |
|
7 {0xCA, 0xFE, 0xBA, 0xBE, 0x00, minor, 0x00, major} |
|
8 |
|
9 major minor Java platform version |
|
10 45 0x27 3 1.0 |
|
11 45 0x27 3 1.1 |
|
12 46 0x28 0 1.2 |
|
13 47 0x29 0 1.3 |
|
14 48 0x30 0 1.4 |
|
15 49 0x31 0 1.5 |
|
16 50 0x32 0 1.6 |
|
17 |
|
18 * Modifiers. |
|
19 |
|
20 ** public. |
|
21 |
|
22 * Public class is visible in other packages. |
|
23 * Public field is visible everywhere (class must be public too). |
|
24 |
|
25 ** private. |
|
26 |
|
27 * Private variables or methods may be used only by an instance of the same |
|
28 class that declares the variable or method |
|
29 * A private feature may only be accessed by the class that owns the feature. |
|
30 |
|
31 ** protected. |
|
32 |
|
33 * Is available to all classes in the same package and also available to all |
|
34 subclasses of the class that owns the protected feature. |
|
35 * This access is provided even to subclasses that reside in a different |
|
36 package from the class that owns the protected feature. |
|
37 |
|
38 ** default. |
|
39 |
|
40 What you get by default ie, without any access modifier. |
|
41 |
|
42 * It means that it is visible to all within a particular package. |
|
43 |
|
44 * static. |
|
45 |
|
46 * Static means one per class, not one for each object no matter how many |
|
47 instance of a class might exist. This means that you can use them without |
|
48 creating an instance of a class. |
|
49 * Static methods are implicitly final, because overriding is done based on |
|
50 the type of the object, and static methods are attached to a class, not an |
|
51 object. |
|
52 * A static method in a superclass can be shadowed by another static method in |
|
53 a subclass, as long as the original method was not declared final. |
|
54 * You can't override a static method with a nonstatic method. |
|
55 |
|
56 * final. |
|
57 |
|
58 * A final class can't be extended ie., final class may not be subclassed. |
|
59 * A final method can't be overridden when its class is inherited. |
|
60 * You can't change value of a final variable. |
|
61 |
|
62 * Exceptions. |
|
63 |
|
64 A checked exception is some subclass of Exception (or Exception itself), |
|
65 excluding class RuntimeException and its subclasses. |
|
66 |
|
67 Unchecked exceptions are RuntimeException and any of its subclasses. Class |
|
68 Error and its subclasses also are unchecked. With an unchecked exception, |
|
69 however, the compiler doesn't force client programmers either to catch the |
|
70 exception or declare it in a throws clause. |
|
71 |
|
72 * Inner classes. |
|
73 |
|
74 ** Nested top-level classes. |
|
75 |
|
76 If you declare a class within a class and specify the static modifier, the |
|
77 compiler treats the class just like any other top-level class. |
|
78 |
|
79 Any class outside the declaring class accesses the nested class with the |
|
80 declaring class name acting similarly to a package. eg, outer.inner. Top-level |
|
81 inner classes implicitly have access only to static variables. There can also |
|
82 be inner interfaces. All of these are of the nested top-level variety. |
|
83 |
|
84 ** Member classes. |
|
85 |
|
86 Member inner classes are just like other member methods and member variables |
|
87 and access to the member class is restricted, just like methods and variables. |
|
88 This means a public member class acts similarly to a nested top-level class. |
|
89 |
|
90 The primary difference between member classes and nested top-level classes is |
|
91 that member classes have access to the specific instance of the enclosing |
|
92 class. |
|
93 |
|
94 ** Local classes. |
|
95 |
|
96 Local classes are like local variables, specific to a block of code. Their |
|
97 visibility is only within the block of their declaration. In order for the |
|
98 class to be useful beyond the declaration block, it would need to implement a |
|
99 more publicly available interface. |
|
100 |
|
101 Because local classes are not members, the modifiers public, protected, |
|
102 private, and static are not usable. |
|
103 |
|
104 ** Anonymous classes. |
|
105 |
|
106 Anonymous inner classes extend local inner classes one level further. As |
|
107 anonymous classes have no name, you cannot provide a constructor. |
|
108 |
|
109 * 64-bit problem. |
|
110 |
|
111 http://www.java.com/en/download/faq/java_win64bit.xml |
|
112 Which version of Java should I download for my 64-bit Windows |
|
113 operating system? |
|
114 http://java.sun.com/javase/6/webnotes/install/system-configurations.html |
|
115 Java SE 6 Release Notes Supported System Configurations |
|
116 |
|
117 * Java performance. |
|
118 |
|
119 http://java.sun.com/performance/reference/whitepapers/5.0_performance.html |
|
120 http://java.sun.com/performance/reference/whitepapers/6_performance.html |
|
121 |
|
122 * Creating jar. |
|
123 |
|
124 $ jar cf myFile.jar *.class |
|
125 |
|
126 $ jar cmf myManifestFile myFile.jar *.class |
|
127 |
|
128 $ jar -cfe Main.jar foo.Main foo/Main.class |
|
129 |
|