设计模式课程 设计模式精讲 3-10 里氏替换原则coding

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 FilesJavajdk1.6.0_43injava.exe" "-javaagent:D:javadevolopKitideaanZhIntelliJ IDEA Community Edition 2018.1.4libidea_rt.jar=17363:D:javadevolopKitideaanZhIntelliJ IDEA Community Edition 2018.1.4in" -Dfile.encoding=UTF-8 -classpath "C:Program FilesJavajdk1.6.0_43jrelibcharsets.jar;C:Program FilesJavajdk1.6.0_43jrelibdeploy.jar;C:Program FilesJavajdk1.6.0_43jrelibextdnsns.jar;C:Program FilesJavajdk1.6.0_43jrelibextlocaledata.jar;C:Program FilesJavajdk1.6.0_43jrelibextsunjce_provider.jar;C:Program FilesJavajdk1.6.0_43jrelibextsunmscapi.jar;C:Program FilesJavajdk1.6.0_43jrelibjavaws.jar;C:Program FilesJavajdk1.6.0_43jrelibjce.jar;C:Program FilesJavajdk1.6.0_43jrelibjsse.jar;C:Program FilesJavajdk1.6.0_43jrelibmanagement-agent.jar;C:Program FilesJavajdk1.6.0_43jrelibplugin.jar;C:Program FilesJavajdk1.6.0_43jrelib
esources.jar;C:Program FilesJavajdk1.6.0_43jrelib
t.jar;F:xiangmu3XinIdeaoutproductiondesign_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 FilesJavajdk1.6.0_43injava.exe" "-javaagent:D:javadevolopKitideaanZhIntelliJ IDEA Community Edition 2018.1.4libidea_rt.jar=21089:D:javadevolopKitideaanZhIntelliJ IDEA Community Edition 2018.1.4in" -Dfile.encoding=UTF-8 -classpath "C:Program FilesJavajdk1.6.0_43jrelibcharsets.jar;C:Program FilesJavajdk1.6.0_43jrelibdeploy.jar;C:Program FilesJavajdk1.6.0_43jrelibextdnsns.jar;C:Program FilesJavajdk1.6.0_43jrelibextlocaledata.jar;C:Program FilesJavajdk1.6.0_43jrelibextsunjce_provider.jar;C:Program FilesJavajdk1.6.0_43jrelibextsunmscapi.jar;C:Program FilesJavajdk1.6.0_43jrelibjavaws.jar;C:Program FilesJavajdk1.6.0_43jrelibjce.jar;C:Program FilesJavajdk1.6.0_43jrelibjsse.jar;C:Program FilesJavajdk1.6.0_43jrelibmanagement-agent.jar;C:Program FilesJavajdk1.6.0_43jrelibplugin.jar;C:Program FilesJavajdk1.6.0_43jrelib
esources.jar;C:Program FilesJavajdk1.6.0_43jrelib
t.jar;F:xiangmu3XinIdeaoutproductiondesign_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 FilesJavajdk1.6.0_43injava.exe" "-javaagent:D:javadevolopKitideaanZhIntelliJ IDEA Community Edition 2018.1.4libidea_rt.jar=21674:D:javadevolopKitideaanZhIntelliJ IDEA Community Edition 2018.1.4in" -Dfile.encoding=UTF-8 -classpath "C:Program FilesJavajdk1.6.0_43jrelibcharsets.jar;C:Program FilesJavajdk1.6.0_43jrelibdeploy.jar;C:Program FilesJavajdk1.6.0_43jrelibextdnsns.jar;C:Program FilesJavajdk1.6.0_43jrelibextlocaledata.jar;C:Program FilesJavajdk1.6.0_43jrelibextsunjce_provider.jar;C:Program FilesJavajdk1.6.0_43jrelibextsunmscapi.jar;C:Program FilesJavajdk1.6.0_43jrelibjavaws.jar;C:Program FilesJavajdk1.6.0_43jrelibjce.jar;C:Program FilesJavajdk1.6.0_43jrelibjsse.jar;C:Program FilesJavajdk1.6.0_43jrelibmanagement-agent.jar;C:Program FilesJavajdk1.6.0_43jrelibplugin.jar;C:Program FilesJavajdk1.6.0_43jrelib
esources.jar;C:Program FilesJavajdk1.6.0_43jrelib
t.jar;F:xiangmu3XinIdeaoutproductiondesign_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();
}