1 代码演练
1.1 继承关系判别(是否是真正意义的继承)
1.2 入参控制
1.3 出参控制
1 代码演练
1.1 继承关系判别(是否是真正意义的继承)(其实我觉得这个例子有点牵强)
1.1.1 反例
结论:
确定继承关系的时候一定要判断好,是否父类的方法子类可以继承。传统意义的正方形是矩形的子类,在这里是不适用的。
测试类1:
package com.geely.design.principle.liskovSubstitutation; public class TestSquare {
public static void resize(Rectangle rectangle){
while(rectangle.getWidth()<=rectangle.getLength()){
rectangle.setWidth(rectangle.getWidth()+1);
System.out.println("长为"+rectangle.getLength()+"****************宽为"+rectangle.getWidth());
} }
public static void main(String [] args){
Rectangle rectangle = new Rectangle();
rectangle.setWidth(10);
rectangle.setLength(20);
resize(rectangle);
} // public static void main(String [] args){
// Square square = new Square();
// square.setLength(10);
// resize(square);
// }
}
打印结果1:
"C:\Program Files\Java\jdk1.6.0_43\bin\java.exe" "-javaagent:D:\java\devolopKit\idea\anZh\IntelliJ IDEA Community Edition 2018.1.4\lib\idea_rt.jar=17363:D:\java\devolopKit\idea\anZh\IntelliJ IDEA Community Edition 2018.1.4\bin" -Dfile.encoding=UTF-8 -classpath "C:\Program Files\Java\jdk1.6.0_43\jre\lib\charsets.jar;C:\Program Files\Java\jdk1.6.0_43\jre\lib\deploy.jar;C:\Program Files\Java\jdk1.6.0_43\jre\lib\ext\dnsns.jar;C:\Program Files\Java\jdk1.6.0_43\jre\lib\ext\localedata.jar;C:\Program Files\Java\jdk1.6.0_43\jre\lib\ext\sunjce_provider.jar;C:\Program Files\Java\jdk1.6.0_43\jre\lib\ext\sunmscapi.jar;C:\Program Files\Java\jdk1.6.0_43\jre\lib\javaws.jar;C:\Program Files\Java\jdk1.6.0_43\jre\lib\jce.jar;C:\Program Files\Java\jdk1.6.0_43\jre\lib\jsse.jar;C:\Program Files\Java\jdk1.6.0_43\jre\lib\management-agent.jar;C:\Program Files\Java\jdk1.6.0_43\jre\lib\plugin.jar;C:\Program Files\Java\jdk1.6.0_43\jre\lib\resources.jar;C:\Program Files\Java\jdk1.6.0_43\jre\lib\rt.jar;F:\xiangmu3\Xin\Idea\out\production\design_pattern" com.geely.design.principle.liskovSubstitutation.TestSquare
长为20****************宽为11
长为20****************宽为12
长为20****************宽为13
长为20****************宽为14
长为20****************宽为15
长为20****************宽为16
长为20****************宽为17
长为20****************宽为18
长为20****************宽为19
长为20****************宽为20
长为20****************宽为21 Process finished with exit code 0
测试类2:
package com.geely.design.principle.liskovSubstitutation; public class TestSquare {
public static void resize(Rectangle rectangle){
while(rectangle.getWidth()<=rectangle.getLength()){
rectangle.setWidth(rectangle.getWidth()+1);
System.out.println("长为"+rectangle.getLength()+"****************宽为"+rectangle.getWidth());
} }
// public static void main(String [] args){
// Rectangle rectangle = new Rectangle();
// rectangle.setWidth(10);
// rectangle.setLength(20);
// resize(rectangle);
// } public static void main(String [] args){
Square square = new Square();
square.setLength(10);
resize(square);
}
}
打印结果2:
**************************************
长为241350****************宽为241350
长为241351****************宽为241351
长为241352****************宽为241352
长为241353****************宽为241353
长为241354****************宽为241354
**************************************
矩形类:
package com.geely.design.principle.liskovSubstitutation; public class Rectangle {
private long length;
private long width; public long getLength() {
return length;
} public void setLength(long length) {
this.length = length;
} public long getWidth() {
return width;
} public void setWidth(long width) {
this.width = width;
}
}
正方形类:
package com.geely.design.principle.liskovSubstitutation; public class Square extends Rectangle {
private long sideLength; public long getSideLength() {
return sideLength;
} public void setSideLength(long sideLength) {
this.sideLength = sideLength;
} @Override
public long getLength() {
return getSideLength();
} @Override
public void setLength(long length) {
setSideLength(length);
} @Override
public long getWidth() {
return getSideLength();
} @Override
public void setWidth(long width) {
setSideLength(width);
}
}
1.1.2 正方形矩形实现四边形
结论:
子类行为规则应与父类行为规则一致,如果子类达不到这一点,则会违背里氏替换原则,违背里氏替换原则会怎样?继承逻辑混乱,代码不便于维护
测试类:
package com.geely.design.principle.liskovSubstitutation; public class TestSquare2 {
public static void resize(Rectangle rectangle){
while(rectangle.getWidth()<=rectangle.getLength()){
rectangle.setWidth(rectangle.getWidth()+1);
System.out.println("长为"+rectangle.getLength()+"****************宽为"+rectangle.getWidth());
} }
// public static void main(String [] args){
// Rectangle rectangle = new Rectangle();
// rectangle.setWidth(10);
// rectangle.setLength(20);
// resize(rectangle);
// } public static void main(String [] args){
Square square = new Square();
square.setSideLength(10);
resize(square);
}
}
四边形接口:
package com.geely.design.principle.liskovSubstitutation; public interface Quadrangle {
long getWidth();
long getLength();
}
矩形类:
package com.geely.design.principle.liskovSubstitutation; public class Rectangle implements Quadrangle{
private long length;
private long width; public void setLength(long length) {
this.length = length;
} public void setWidth(long width) {
this.width = width;
} @Override
public long getWidth() {
return width;
} @Override
public long getLength() {
return length;
}
}
正方形类:
package com.geely.design.principle.liskovSubstitutation; public class Square implements Quadrangle{
private long sideLength; public long getSideLength() {
return sideLength;
}
public void setSideLength(long sideLength) {
this.sideLength = sideLength;
} @Override
public long getWidth() {
return sideLength;
} @Override
public long getLength() {
return sideLength;
}
}
1.2 入参控制
1.2.1 里氏替换原则正例
结论:
重载的时候入参更加宽松,可以不引起逻辑的混乱。
测试类:
package com.geely.design.principle.liskovSubstitutation.inputmethod; import java.util.HashMap; public class TestChild {
public static void main(String [] args){
Child child = new Child();
HashMap hashMap = new HashMap();
child.method(hashMap);
}
}
子类:
import java.util.HashMap;
import java.util.Map; public class Child extends Base{
// @Override
// public void method(HashMap hashMap) {
// System.out.println("执行子类的HashMap方法");
// } /**
* 子类重载
* 重载的时候入参 Map比 Hashmap宽松,此时执行的时候会执行父类,不执行重载的类
* @param hashMap
*/
public void method(Map Map) {
System.out.println("执行子类Map方法");
}
}
父类:
package com.geely.design.principle.liskovSubstitutation.inputmethod; import java.util.HashMap; public class Base {
public void method(HashMap hashMap){
System.out.println("执行父类HashMap方法");
} }
打印结果:
"C:\Program Files\Java\jdk1.6.0_43\bin\java.exe" "-javaagent:D:\java\devolopKit\idea\anZh\IntelliJ IDEA Community Edition 2018.1.4\lib\idea_rt.jar=21089:D:\java\devolopKit\idea\anZh\IntelliJ IDEA Community Edition 2018.1.4\bin" -Dfile.encoding=UTF-8 -classpath "C:\Program Files\Java\jdk1.6.0_43\jre\lib\charsets.jar;C:\Program Files\Java\jdk1.6.0_43\jre\lib\deploy.jar;C:\Program Files\Java\jdk1.6.0_43\jre\lib\ext\dnsns.jar;C:\Program Files\Java\jdk1.6.0_43\jre\lib\ext\localedata.jar;C:\Program Files\Java\jdk1.6.0_43\jre\lib\ext\sunjce_provider.jar;C:\Program Files\Java\jdk1.6.0_43\jre\lib\ext\sunmscapi.jar;C:\Program Files\Java\jdk1.6.0_43\jre\lib\javaws.jar;C:\Program Files\Java\jdk1.6.0_43\jre\lib\jce.jar;C:\Program Files\Java\jdk1.6.0_43\jre\lib\jsse.jar;C:\Program Files\Java\jdk1.6.0_43\jre\lib\management-agent.jar;C:\Program Files\Java\jdk1.6.0_43\jre\lib\plugin.jar;C:\Program Files\Java\jdk1.6.0_43\jre\lib\resources.jar;C:\Program Files\Java\jdk1.6.0_43\jre\lib\rt.jar;F:\xiangmu3\Xin\Idea\out\production\design_pattern" com.geely.design.principle.liskovSubstitutation.inputmethod.TestChild
执行父类HashMap方法 Process finished with exit code 0
1.2.2 里氏替换原则反例
测试类:
package com.geely.design.principle.liskovSubstitutation.inputmethod; import java.util.HashMap; public class TestChild {
public static void main(String [] args){
Child child = new Child();
HashMap hashMap = new HashMap();
child.method(hashMap);
}
}
子类:
package com.geely.design.principle.liskovSubstitutation.inputmethod; import java.util.HashMap;
import java.util.Map; public class Child extends Base{
// @Override
// public void method(Map map) {
// super.method(map);
// } public void method(HashMap hashMap) {
System.out.println("执行子类HashMap方法");
}
}
父类:
package com.geely.design.principle.liskovSubstitutation.inputmethod; import java.util.HashMap;
import java.util.Map; public class Base {
public void method(Map map){
System.out.println("执行父类HashMap方法");
} }
打印日志:
"C:\Program Files\Java\jdk1.6.0_43\bin\java.exe" "-javaagent:D:\java\devolopKit\idea\anZh\IntelliJ IDEA Community Edition 2018.1.4\lib\idea_rt.jar=21674:D:\java\devolopKit\idea\anZh\IntelliJ IDEA Community Edition 2018.1.4\bin" -Dfile.encoding=UTF-8 -classpath "C:\Program Files\Java\jdk1.6.0_43\jre\lib\charsets.jar;C:\Program Files\Java\jdk1.6.0_43\jre\lib\deploy.jar;C:\Program Files\Java\jdk1.6.0_43\jre\lib\ext\dnsns.jar;C:\Program Files\Java\jdk1.6.0_43\jre\lib\ext\localedata.jar;C:\Program Files\Java\jdk1.6.0_43\jre\lib\ext\sunjce_provider.jar;C:\Program Files\Java\jdk1.6.0_43\jre\lib\ext\sunmscapi.jar;C:\Program Files\Java\jdk1.6.0_43\jre\lib\javaws.jar;C:\Program Files\Java\jdk1.6.0_43\jre\lib\jce.jar;C:\Program Files\Java\jdk1.6.0_43\jre\lib\jsse.jar;C:\Program Files\Java\jdk1.6.0_43\jre\lib\management-agent.jar;C:\Program Files\Java\jdk1.6.0_43\jre\lib\plugin.jar;C:\Program Files\Java\jdk1.6.0_43\jre\lib\resources.jar;C:\Program Files\Java\jdk1.6.0_43\jre\lib\rt.jar;F:\xiangmu3\Xin\Idea\out\production\design_pattern" com.geely.design.principle.liskovSubstitutation.inputmethod.TestChild
执行子类HashMap方法 Process finished with exit code 0
1.3 出参控制
1.3.1 反例
结论:
子类的出参如果包含父类,会直接报错。
子类:
package com.geely.design.principle.liskovSubstitutation.outputmethod; import java.util.Map; public class Child extends Base {
@Override
public Object method() {
return null;
}
}
父类:
package com.geely.design.principle.liskovSubstitutation.outputmethod; import java.util.Map; public abstract class Base {
public abstract Map method();
}