7.2 what
一個軟件實體如果使用的是一個基類的話，那么一定適用于其子類，而且它根本不能覺察出基類對象和子類對象的區別。
反之不成立。

7.3 在設計模式中的體現
策略模式
合成模式
代理模式

7.5
長方形和正方形
Rectangle類的源代碼：
?1package?com.javapatterns.liskov.version1;
?2
?3public?class?Rectangle
?4{
?5????private?long?width;
?6????private?long?height;
?7????
?8????public?void?setWidth(long?width)
?9????{
10????????this.width?=?width;
11????}
12????public?long?getWidth()
13????{
14????????return?this.width;
15????}
16????public?void?setHeight(long?height)
17????{
18????????this.height?=?height;
19????}
20????public?long?getHeight()
21????{
22????????return?this.height;
23????}
24}

Square類的源代碼：
?1package?com.javapatterns.liskov.version1;
?2
?3public?class?Square
?4{
?5????private?long?side;
?6????
?7????public?void?setSide(long?side)
?8????{
?9????????this.side?=?side;
10????}
11
12????public?long?getSide()
13????{
14????????return?side;
15????}
16}

正方形不可以作為長方形的子類
新的Square類的源代碼：
?1package?com.javapatterns.liskov.version2;
?2
?3public?class?Square?extends?Rectangle
?4{
?5????private?long?side;
?6
?7????public?void?setWidth(long?width)
?8????{
?9????????setSide(width);
10????}
11
12????public?long?getWidth()
13????{
14????????return?getSide();
15????}
16
17????public?void?setHeight(long?height)
18????{
19????????setSide(height);
20????}
21
22????public?long?getHeight()
23????{
24????????return?getSide();
25????}
26
27????public?long?getSide()
28????{
29????????return?side;
30????}
31
32????public?void?setSide(long?side)
33????{
34????????this.side?=?side;
35????}
36}

SmartTest類的源代碼：
?1package?com.javapatterns.liskov.version2;
?2
?3public?class?SmartTest
?4{
?5????public?void?resize(Rectangle?r)
?6????{
?7????????while?(r.getHeight()?<=?r.getWidth()?)
?8????????{
?9????????????r.setWidth(r.getWidth()?+?1);
10????????}
11????}
12
13????/**?@link?dependency?*/
14????/*#Rectangle?lnkRectangle;*/
15}

代碼的重構
Quadrangle類的源代碼：
1package?com.javapatterns.liskov.version3;
2
3public?interface?Quadrangle
4{
5????public?long?getWidth();
6
7????public?long?getHeight();
8}

Rectangle類的源代碼：
?1package?com.javapatterns.liskov.version3;
?2
?3public?class?Rectangle?implements?Quadrangle?
?4{
?5????private?long?width;
?6????private?long?height;
?7????
?8????public?void?setWidth(long?width)
?9????{
10????????this.width?=?width;
11????}
12????public?long?getWidth()
13????{
14????????return?this.width;
15????}
16????public?void?setHeight(long?height)
17????{
18????????this.height?=?height;
19????}
20????public?long?getHeight()
21????{
22????????return?this.height;
23????}
24}

Square類的源代碼：?
?1package?com.javapatterns.liskov.version3;
?2
?3public?class?Square?implements?Quadrangle?
?4{
?5????private?long?side;
?6
?7????public?void?setSide(long?side)
?8????{
?9????????this.side?=?side;
10????}
11
12????public?long?getSide()
13????{
14????????return?side;
15????}
16
17????public?long?getWidth()
18????{
19????????return?getSide();
20????}
21
22????public?long?getHeight()
23????{
24????????return?getSide();
25????}
26}

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