Java程序设计英文版课件：ch6 Access Control.ppt

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Chapter 6
Access Control
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　Why Java support Access Control
Machine Language
Assembly language
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　Why Java support Access Control
“separating the things that change from the things that stay the same.”
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　Why Java support Access Control
Access Control
“separating the things that change from the things that stay the same.”
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　Why Java support Access Control
Public
Protected
Private
Package
import
Access Control
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Package: the library unit
Import Statement
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Package: the library unit
.java
Only one public class
class
class
.class
.class
.class
compilation unit
public class: There can be one and there can be only one in each compilation unit.
public class name: the same name as the file (including capitalization, but excluding the .java filename extension).
additional classes: support main public class.
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Package: the library unit

library


If you use a package statement, it must appear as the first noncomment in the file.
Note that the convention for Java package names is to use all lowercase letters, even for intermediate words.
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Package: the library unit





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Package: the library unit
Package
\net\mindview\simple\
C:\DOC\JavaT\net\mindview\simple\
C:\DOC\JavaT\net\mindview\simple\
Java interpreter
CLASSPATH
.class file
directory