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Want to use Enum file name dynamically to fetch constants

I have a config file with key value pair as
language = "IN"
and i have multiple page object enum files with name as
PageObject_US,PageObject_UK,PageObject_IN
every page object enum file has constants that can be accessed using for example
PageObjects_US.String.lable
but what i want to achieve is a way to create something like below
take the parameter from config file store it in a string
like String language = "IN"
Then concatenate using "PageObjects_" + language to get (PageObjects_IN)
so that the returned value can be used to fetch the constants from PageObjects_IN.String.label.
following is the code block:
if(!ENV.equalsIgnoreCase("development") && VALIDATION.equalsIgnoreCase("yes")) {
Elements.ByTitle(webDriver,PageObjects_IN.GREAT.label);
Elements.ByID(webDriver, PageObjects_IN.COUNTER.label);
}
In the above i want to use enum file PageObjects_IN at run time as i have many enum files
below is the enum
public enum PageObjects_IN {
// Text
GREAT("great"),
COUNTER("counter");
public final String lable;
PageObjects_IN(final String lable) {
this.lable = lable;
}
}

This is possible (using reflection) but strongly not recommended as it eliminates the efficiency of Java language constructs.
Not recommended way
Say you have a package click.webelement.cucumber.po where you store
public enum PO_EN {
GREAT("great_en"),
COUNTER("counter_en");
public final String label;
PO_EN(String label){
this.label = label;
}
}
and
public enum PO_IN {
GREAT("great_in"),
COUNTER("counter_in");
public final String label;
PO_IN(String label){
this.label = label;
}
}
Then to take a value you can do something like this:
String lang = "EN";
// Take class
Class clazz = Class.forName("click.webelement.cucumber.po.PO_" + lang);
// Find an object that represent enum constant
Object val = Arrays
.stream(clazz.getEnumConstants()).filter(o -> "GREAT".equals(o.toString()))
.findAny()
.get();
// Take field value for that object
Field f = clazz.getField("label");
System.out.println(f.get(val));
This is error-prone approach and you would not have benefit from compile phase.
Recommended approach - 1
Instead of having enum use classes.
public abstract class PO {
public abstract String great();
public abstract String counter();
}
and
public class PO_EN extends PO{
#Override
public String great() {
return "great_en";
}
#Override
public String counter() {
return "counter_en";
}
}
and
public class PO_IN extends PO{
#Override
public String great() {
return "great_in";
}
#Override
public String counter() {
return "counter_in";
}
}
so your test would be much simpler
String lang = "EN";
Class clazz = Class.forName("click.webelement.cucumber.po.PO_" + lang);
PO val = (PO) clazz.getDeclaredConstructor().newInstance();
System.out.println(val.great());
Recommended approach - 2
You can utilize PageFactory harness for your page objects and use this lib to parametrize your locators, like (if you use test ng):
#DataProvider(name = "languages")
Object[][] dataProvider(){
return new Object[][]{
{"en", "great_en", "counter_en"},
{"in", "great_in", "counter_in"}
};
}
#Test(dataProvider = "languages")
public void testPage(String language, String great, String counter){
DefaultParameterProvider
.properties
.set(Map.of("p.great", great, "p.counter", counter));
MyPage myPage = new MyPage(driver);
...
}
Where your page would be like this:
public class MyPage extends PageObjectParameterized {
#FindByParameterized(xpath = "//button[#name='{wec:p.great}']")
WebElement great;
#FindByParameterized(xpath = "//label[text()='{wec:p.counter}']")
WebElement counter;
#FindBy(xpath = "//input")
WebElement input;
public MyPage(SearchContext searchContext) {
super(searchContext);
}
}

Java - how to call a method of corresponding class based on string using enum/factory pattern

Yes, I read many examples in web, but I didn't find a way how to call a method based on string value. May be I am not searching in right way... I wrote all code, but don't know how to call the method.
fyi: I don't want to use if else or switch case
Here is what I want:
I get the card reader type as String from database. I have to call the corresponding class' method.
My code:
LoginPanel.java
public class LoginPanel {
public static void main(String args[]) {
String readerType = "Omnikey5427-CK"; // I get this ("Omnikey5427-CK" or "Omnikey5427-G2") from a database as String
// I WANT TO CALL getCardNumber() method of respective class
}
}
ISmartCardReader.java
public interface ISmartCardReader {
public Integer getCardNumber();
}
Omnikey5427G2.java
public class Omnikey5427G2 implements ISmartCardReader {
public Omnikey5427G2() {
System.out.println("G222222222222222...");
}
public Integer getCardNumber() {
return 222;
}
}
Omnikey5427CK.java
public class Omnikey5427CK implements ISmartCardReader {
public Omnikey5427CK() {
System.out.println("CKKKKKKKKKKKKKKK...");
}
public Integer getCardNumber() {
return 111;
}
}
SmacrtCardEnumFactory.java
public enum SmacrtCardEnumFactory {
OMNIKEY5427CK("Omnikey5427-CK") {
public ISmartCardReader geInstance() {
return new Omnikey5427CK();
}
},
OMNIKEY5427G2("Omnikey5427-G2") {
public ISmartCardReader geInstance() {
return new Omnikey5427G2();
}
};
private String cardReaderName;
private SmacrtCardEnumFactory(String cardReaderName) {
this.cardReaderName = cardReaderName;
}
public String cardReaderName() {
return cardReaderName;
}
}

You can use valueOf() function of enum provided your enum sonstant names match strings used to lookup (you may use cardName.toUpper()). You may also create objects for all the card types and store them in a hash map and then lookup them. You can also write some fatory method, but this will be if-then-else or switch inside

You could iterate over the factory's values() and get the one that matches the string:
public enum SmacrtCardEnumFactory {
// current code omitted for brevity
public static getSmartCardReader(String name) {
return Arrays.stream(values())
.filter(r -> r.cardReaderName().equals(name))
.map(SmacrtCardEnumFactory::getInstance();
.orElse(null);
}
}

Using a fluent builder pattern without inner static classes for workflow

This is a continuation from what I was working in Passing 1 to many parameters of same object type
I've gotten good feedback on that , I believe i have the improved the design . The whole code is at https://github.com/spakai/flow_input_builder
The requirement is simple : -
I need to build a set of input for different workflows using 1 or more outputs from previous workflows
I have a set of interfaces
public interface SwfInput {
}
public interface SwfOutput {
}
public interface Workflow<I extends SwfInput, O extends SwfOutput> {
public O execute(I input);
}
public interface Builder<I extends SwfInput> {
public I build();
}
Now , Say I have 3 flows which gets executed in sequence FlowA->FlowB->FlowC
FlowC needs mandatory output from FlowB but only optionally from FlowA
so I have a implementation for FlowCBuilder
public class FlowCInputBuilder implements Builder<FlowCInput> {
private final FlowBOutput mandatoryflowBOutput;
private FlowAOutput optionalflowAOutput;
public FlowAOutput getOptionalflowAOutput() {
return optionalflowAOutput;
}
public FlowCInputBuilder setOptionalflowAOutput(FlowAOutput optionalflowAOutput) {
this.optionalflowAOutput = optionalflowAOutput;
return this;
}
public FlowCInputBuilder(FlowBOutput mandatoryflowBOutput) {
this.mandatoryflowBOutput = mandatoryflowBOutput;
}
#Override
public FlowCInput build() {
FlowCInput input = new FlowCInput();
input.setMandatoryFromFlowB(mandatoryflowBOutput.getOutput1FromB());
if (optionalflowAOutput != null) {
input.setOptionalFromFlowA(optionalflowAOutput.getOutput2FromA());
}
return input;
}
}
one test i have written shows an example usage
FlowBOutput mandatoryflowBOutput = new FlowBOutput();
mandatoryflowBOutput.setOutput1FromB("iNeedThis");
FlowAOutput optionalflowAOutput = new FlowAOutput();
FlowCInput input = new FlowCInputBuilder(mandatoryflowBOutput)
.setOptionalflowAOutput(optionalflowAOutput)
.build();
I have not used static inner class for the Builder pattern.
Any suggestions are welcomed.

You should use static inner class. The key point of using this approach is that, the inner can directly access private properties of the object being constructed. This helps eliminating duplicated code since the builder does not need to maintain a long list of temporary state for the constructing. So, your code can be rewritten like this:
public class FlowCInput {
private int output1FromB; // suppose that it is int
private String output2FromA; // suppose that it is String
private FlowCInput() { }
//...
public static class FlowCInputBuilder implements Builder<FlowCInput> {
private final FlowCInput result;
public FlowCInputBuilder(FlowBOutput mandatoryflowBOutput) {
result = new FlowCInput();
// output1FromB is private but still accessed from here
result.output1FromB = mandatoryflowBOutput.getOutput1FromB();
}
public FlowCInputBuilder setOptionalflowAOutput(FlowAOutput optionalflowAOutput) {
// same for output2FromA
result.output2FromA = optionalflowAOutput.getOutput2FromA();
return this;
}
#Override
public FlowCInput build() {
return result;
}
}
}
As you see, the builder now holds only a FlowCInput object, it does not unnecessarily hold mandatoryflowBOutput and optionalflowAOutput as before.

Replacing if else statement with pattern

I have a if else statement which might grow in the near future.
public void decide(String someCondition){
if(someCondition.equals("conditionOne")){
//
someMethod("someParameter");
}else if(someCondition.equals("conditionTwo")){
//
someMethod("anotherParameter");
}
.
.
else{
someMethod("elseParameter");
}
}
Since, this is already looking messy, I think it would be better if I can apply any design patterns here. I looked into Strategy pattern but I am not sure if that will reduce if else condition here. Any suggestions?

This is a classic Replace Condition dispatcher with Command in the Refactoring to Patterns book.
Basically you make a Command object for each of the blocks of code in your old if/else group and then make a Map of those commands where the keys are your condition Strings
interface Handler{
void handle( myObject o);
}
Map<String, Handler> commandMap = new HashMap<>();
//feel free to factor these out to their own class or
//if using Java 8 use the new Lambda syntax
commandMap.put("conditionOne", new Handler(){
void handle(MyObject o){
//get desired parameters from MyObject and do stuff
}
});
...
Then instead of your if/else code it is instead:
commandMap.get(someCondition).handle(this);
Now if you need to later add new commands, you just add to the hash.
If you want to handle a default case, you can use the Null Object pattern to handle the case where a condition isn't in the Map.
Handler defaultHandler = ...
if(commandMap.containsKey(someCondition)){
commandMap.get(someCondition).handle(this);
}else{
defaultHandler.handle(this);
}

Let's assume that we have such code (which is the same as yours):
public void decide(String someCondition) {
if(someCondition.equals("conditionOne")) {
someMethod("someParameter");
}
else if(someCondition.equals("conditionTwo")) {
someMethod("anotherParameter");
}
else {
someMethod("elseParameter");
}
}
Assuming that you don't want to refactor other parts of the application and you don't want to change method signature there are possible ways in which it could be refactored:
Warning - You should use generic versions of mentioned patterns.
I showed non generic ones because it is easier to read them.
Strategy + Factory Method
We can use Strategy and Factory Method patterns. We also take advantage of polymorphism.
private final StrategyConditionFactory strategyConditionFactory = new StrategyConditionFactory();
public void decide(String someCondition) {
Strategy strategy = strategyConditionFactory.getStrategy(someCondition)
.orElseThrow(() -> new IllegalArgumentException("Wrong condition"));
strategy.apply();
}
It would be better to design it in a way that else condition is included in the factory, and developer calls it on purpose. In such case we throw exception when condition is not meet. Alternatively we could write it exactly as it was in question. If you want so instead of .orElseThrow(() -> new IllegalArgumentException("Wrong condition")); put .orElse(new ElseStrategy());
StrategyConditionFactory (factory method):
public class StrategyConditionFactory {
private Map<String, Strategy> conditions = new HashMap<>();
public StrategyConditionFactory() {
conditions.put("conditionOne", new ConditionOneStrategy());
conditions.put("conditionTwo", new ConditionTwoStrategy());
//It is better to call else condition on purpose than to have it in the conditional method
conditions.put("conditionElse", new ElseStrategy());
//...
}
public Optional<Strategy> getStrategy(String condition) {
return Optional.ofNullable(conditions.get(condition));
}
}
Strategy interface:
public interface Strategy {
void apply();
}
Implementations:
public class ConditionOneStrategy implements Strategy {
#Override
public void apply() {
//someMethod("someParameter");
}
}
public class ConditionTwoStrategy implements Strategy {
#Override
public void apply() {
//someMethod("anotherParameter")
}
}
public class ElseStrategy implements Strategy {
#Override
public void apply() {
//someMethod("elseParameter")
}
}
Usage (simplified):
public void strategyFactoryApp() {
//...
decide("conditionOne");
decide("conditionTwo");
decide("conditionElse");
//...
}
Strategy + Factory Method - this particular case (where only parameter changes)
We can use the fact that in this case we always call the same method, only parameter changes
We change our base strategy interface to abstract class with getParameter() method and we make new implementations of this abstract class. Other code remains the same.
public abstract class Strategy {
public abstract String getParameter();
public void apply() {
someMethod(getParameter());
}
private void someMethod(String parameter) {
//someAction
}
}
Implementations:
public class CondtionOneStrategy extends Strategy {
#Override
public String getParameter() {
return "someParameter";
}
}
public class CondtionTwoStrategy extends Strategy {
#Override
public String getParameter() {
return "anotherParameter";
}
}
public class ElseStrategy extends Strategy {
#Override
public String getParameter() {
return "elseParameter";
}
}
Enum + enum kinda "factory"
We might use Enum to implement strategy and instead of factory method we can use valueOf() from enum.
public void decide(String someCondition) {
ConditionEnum conditionEnum = ConditionEnum.valueOf(someCondition);
conditionEnum.apply();
}
Condition enum:
public enum ConditionEnum {
CONDITION_ONE {
#Override
public void apply() {
//someMethod("someParameter");
}
},
CONDITION_TWO {
#Override
public void apply() {
//someMethod("anotherParameter");
}
},
CONDITION_ELSE {
#Override
public void apply() {
//someMethod("elseParameter");
}
};
//...more conditions
public abstract void apply();
}
Usage (simplified):
public void enumFactoryApp() {
//...
decide("CONDITION_ONE");
decide("CONDITION_TWO");
decide("CONDITION_ELSE");
//...
}
Notice that you will get IllegalArgumentException when enum type has no constant with the specified name.
Command + Factory
The difference between strategy and command is that command holds also state, so if you have for example compute(int a, int b, String someCondition) and you want to refactor it with strategy including it's signature change you can reduce it to compute(int a, int b, ComputeStrategy computeStrategy) with command you can reduce it to one argument compute(ComputeCommand computeCommand). In this case we also take advantage of polymorphism similarly to strategy pattern case.
CommandConditionFactory commandConditionFactory = new CommandConditionFactory();
public void decide(String someCondition) {
Command command = commandConditionFactory.getCommand(someCondition)
.orElseThrow(() -> new IllegalArgumentException("Wrong condition"));
command.apply();
}
It would be better to design it in a way that else condition is included in the factory, and developer calls it on purpose. In such case we throw exception when condition is not meet. Alternatively we could write it exactly as it was in question. If you want so instead of .orElseThrow(() -> new IllegalArgumentException("Wrong condition")); put .orElse(new ElseCommand());
CommandConditionFactory (factory method):
public class CommandConditionFactory {
private Map<String, Command> conditions = new HashMap<>();
public CommandConditionFactory() {
conditions.put("conditionOne", new ConditionOneCommand("someParameter"));
conditions.put("conditionTwo", new ConditionTwoCommand("anotherParameter"));
//It is better to call else condition on purpose than to have it in the conditional method
conditions.put("conditionElse", new ElseCommand("elseParameter"));
//...
}
public Optional<Command> getCommand(String condition) {
return Optional.ofNullable(conditions.get(condition));
}
}
Command interface:
public interface Command {
void apply();
}
Implementations (there is some redundancy, but It is there to show how command should look in more general case where instead of someMethod() we have three different methods):
public class ConditionOneCommand implements Command {
private final String parameter;
public ConditionOneCommand(String parameter) {
this.parameter = parameter;
}
#Override
public void apply() {
//someMethod(parameter);
}
}
public class ConditionTwoCommand implements Command {
private final String parameter;
public ConditionTwoCommand(String parameter) {
this.parameter = parameter;
}
#Override
public void apply() {
//someMethod(parameter);
}
}
public class ElseCommand implements Command {
private final String parameter;
public ElseCommand(String parameter) {
this.parameter = parameter;
}
#Override
public void apply() {
//someMethod(parameter);
}
}
Usage (simplified):
public void commandFactoryApp() {
//...
decide("conditionOne");
decide("conditionTwo");
decide("conditionElse");
//...
}
Command + Factory - This particular case.
This in fact isn't a real command pattern just a derivative. It takes advantage of the fact that in this case we are always calling the same method someMethod(parameter) and only the parameter changes.
Abstract class:
public abstract class Command {
abstract void apply();
protected void someMethod(String parameter) {
//someAction
}
}
Implementation (the same for all 3 conditional cases):
public class CommandImpl extends Command {
private final String parameter;
public CommandImpl (String parameter) {
this.parameter = parameter;
}
#Override
public void apply(){
someMethod(parameter);
}
}
Factory, please notice that there is only one command implementation, only parameter changes:
public class CommandConditionFactory {
Map<String, Command> conditions = new HashMap<>();
public CommandConditionFactory() {
conditions.put("conditionOne", new CommandImpl("someParameter"));
conditions.put("conditionTwo", new CommandImpl("anotherParameter"));
//It is better to call else condition on purpose than to have it in the conditional method
conditions.put("conditionElse", new CommandImpl("elseParameter"));
//...
}
public Optional<Command> getCommand(String condition) {
return Optional.ofNullable(conditions.get(condition));
}
}
Nested if's
Note that even if you have nested ifs sometimes it is possible to refactor them and use one of the mentioned techniques.
Lets say that we have following code:
public void decide2(String someCondition, String nestedCondition) {
if(someCondition.equals("conditionOne")) {
if(nestedCondition.equals("nestedConditionOne")){
someLogic1();
}
else if(nestedCondition.equals("nestedConditionTwo")){
someLogic2();
}
}
else if(someCondition.equals("conditionTwo")) {
if(nestedCondition.equals("nestedConditionThree")){
someLogic3();
}
else if(nestedCondition.equals("nestedConditionFour")){
someLogic4();
}
}
}
You could refactor it using mathematical logic rules:
public void decide2(String someCondition, String nestedCondition) {
if(someCondition.equals("conditionOne")
&& nestedCondition.equals("nestedConditionOne")) {
someLogic1();
}
else if(someCondition.equals("conditionOne")
&& nestedCondition.equals("nestedConditionTwo")) {
someLogic2();
}
else if(someCondition.equals("conditionTwo")
&& nestedCondition.equals("nestedConditionThree")) {
someLogic3();
}
else if(someCondition.equals("conditionTwo")
&& nestedCondition.equals("nestedConditionFour")) {
someLogic4();
}
}
and then you can use strategy, enum or command. You just have a pair of Strings <String, String> instead of single String.
Decision Tables
When you have nested ifs that couldn't be refactored as mentioned you can implement your own decision tables or use some ready to go decision tables solution. I won't give the implementation there.
Rules Engine
When you have nested ifs that couldn't be refactored as mentioned you can also implement your own simple rules engine. You should use it only if you have many nested ifs, otherwise it is triumph of form over content.
For very complicated Business Logic there are professional Rule Engines like Drools.
I won't give the implementation there.
One more thing
In the example that you gave there is a high possibility that someone introduced these ifs, but they are totally redundant. And we can check it by trying to refactor decide method signature to make it take some other argument and to refactor surrounding code that is calling our method. By doing so we are getting rid of our Factory Method. There are examples that present how the code might look when it occurs that these ifs were redundant.
Strategy
Decide method:
public void decide(Strategy strategy) {
strategy.apply();
}
Usage (simplified):
public void strategyApp() {
//...
decide(new ConditionOneStrategy());
decide(new ConditionTwoStrategy());
decide(new ElseStrategy());
//...
}
Enum
Decide method:
public void decide(ConditionEnum conditionEnum) {
conditionEnum.apply();
}
Usage (simplified):
public void enumApp() {
//...
decide(ConditionEnum.CONDITION_ONE);
decide(ConditionEnum.CONDITION_TWO);
decide(ConditionEnum.CONDITION_ELSE);
//...
}
Command
Decide method:
public void decide(Command command) {
command.apply();
}
Usage (simplified):
public void commandApp() {
//...
decide(new ConditionOneCommand("someParameter"));
decide(new ConditionTwoCommand("anotherParameter"));
decide(new ElseCommand("elseParameter"));
//...
}
In fact it is quite specific case, there are cases in which for example we have to use simple type like String, because it comes from the external system or condition is based on integer from input so we can't refactor the code so easily.

The general recommendation by Martin Fowler is to
Replace Conditional with Polymorphism.
In terms of design patterns this would often be the Strategy Pattern
Replace Conditional Logic with Strategy.
If you have a small, finite set of conditions, I recommend to use an enum to implement the Strategy Pattern (provide an abstract method in the enum and override it for each constant).
public enum SomeCondition{
CONDITION_ONE{
public void someMethod(MyClass myClass){
//...
}
},
CONDITION_TWO{
public void someMethod(MyClass myClass){
}
}
public abstract void someMethod(MyClass myClass);
}
public class MyClass{
//...
public void decide(SomeCondition someCondition){
someCondition.someMethod(this);
}
}
If it's really just a parameter you want to pick, then you could define the enum like this instead:
public enum SomeCondition{
CONDITION_ONE("parameterOne"),
CONDITION_TWO("parameterTwo");
private final String parameter;
private SomeCondition(String parameter){
this.parameter = parameter;
}
public String getParameter(){
return parameter;
}
}
public class MyClass{
//...
public void decide(SomeCondition someCondition){
someMethod(someCondition.getParameter());
}
}

Another way to solve the current problem is to use Factory Pattern. This provides functionality to extract a factory method that returns an object of a given type and performs the operation based on the concrete object behavior.
public interface Operation {
String process(String a, String b);
}
The method takes two string as input and returns the result.
public class Concatenation implements Operation {
#Override
public String process(String a, String b) {
return a.concat(b);
}
}
public class Join implements Operation {
#Override
public String process(String a, String b) {
return String.join(", ", a, b);
}
}
And then we should define a factory class which returns instances of Operation based on the given operator:
public class OperatorFactory {
static Map<String, Operation> operationMap = new HashMap<>();
static {
operationMap.put("concatenation", new Concatenation());
operationMap.put("join", new Join());
// more operators
}
public static Optional<Operation> getOperation(String operator) {
return Optional.ofNullable(operationMap.get(operator));
}
}
And now we can use it:
public class SomeServiceClass {
public String processUsingFactory(String a, String b, String operationName) {
Operation operation = OperatorFactory
.getOperation(operationName)
.orElseThrow(() -> new IllegalArgumentException("Invalid Operation"));
return operation.process(a, b);
}
}

I guess you must have already considered it, but if you are using JDK 7 or above, you can switch on strings. That way your code can look cleaner than a bunch of if-else statements.

Improve code with several booleans conditions java

I got a big problem to deal with, my code is too long and full characters. I removed a lot, using methods and using some proper design patterns... But it is still too "crowded".
I get a string from the user, a question like:
"How are you Josh?"
"Who is Josh's mother?"
I need to analyze that question so see it's content and to System.out.print() the answer.
so a long serie of "if/else if" starts e.g
if (question.startsWith("How") && question.endsWith("Josh?"))
{
//do a lot of things here.
System.out.print(actualHealth);
}
else if (question.startsWith("Who") && question.endsWith("mother?"))
{
//do a lot of things here.
System.out.print(getParents().getMother());
}
*
*
* //Lot of "else if" here to recognize the question meaning.
*
*
else
{
System.out.print("question not recognized");
}
I called this class AnswersFactory as referred to the Design Pattern "Factory Pattern" because the question, is "asked" in another class. But I suppose it's a wrong way to consider it a design pattern.
How to simplify all those conditions even if they seem impossible to simplify, or at least make the code seem more organized? Is there a good design pattern to follow?
My code works great but is not beautiful to see. I hope you understand that frustration!
Thank you.

Not sure why you want to check the question based on the keyword, it has some drawbacks like mentioned by HCBPshenanigans
But to change it to be more flexible, I would do something like this:
An interface for all question handlers
public interface IQuestionHandler
{
bool CanHandle(string question);
void Handle(string question);
}
Concrete class for each scenario. Each class will tell whether it can handle the question or not, and contain logic to handle the question:
public class HealthQuestionHandler : IQuestionHandler
{
public bool CanHandle(string question)
{
return question.StartsWith("How") && question.EndsWith("Josh?");
}
public void Handle(string question)
{
//Replace by actual processing
string healthStatus = "I'm fine";
Console.WriteLine(healthStatus);
}
}
public class MotherQuestionHandler : IQuestionHandler
{
public bool CanHandle(string question)
{
return question.StartsWith("Who") && question.EndsWith("mother?");
}
public void Handle(string question)
{
//Replace by actual processing
string mother = "...";
Console.WriteLine(mother);
}
}
And finally a question handler processor to manage all the handlers. It will register all available handlers in constructor. When called to process, it goes through all of available handlers, ask one by one which one can handle the question
public class QuestionHandlerProcessor
{
private List<IQuestionHandler> _handlers;
public QuestionHandlerProcessor()
{
//Register available handlers
_handlers = new List<IQuestionHandler>
{
new HealthQuestionHandler(),
new MotherQuestionHandler()
};
}
public void Process(string question)
{
foreach(var handler in _handlers)
{
if(handler.CanHandle(question))
{
handler.Handle(question);
return;
}
}
Console.WriteLine("Question not recognized");
}
}
Usage:
QuestionHandlerProcessor processor = new QuestionHandlerProcessor();
processor.Process("How are you Josh?");
processor.Process("Who is Josh's mother?");
Although my answer is in C#, but should not be difficult to convert to Java.

you can use Chain Of Responsibility pattern. you will need catching the exception
UnhandledQuestionException
.
public abstract class QuestionHandler {
protected QuestionHandler successor;
public void setSuccessor(QuestionHandler successor) {
this.successor = successor;
}
public abstract void handle(String question);
}
and implementors should be so
public class HealthQuestionHandler extends QuestionHandler {
private bool canHandle(String question) {
return question.startsWith("How") && question.endsWith("Josh");
}
public void handle(String question) {
if( canHandle(question) ) {
String healthStatus = "I am fine";
System.out.println(healthStatus);
} else {
super.successor.handle(question);
}
}
}
public class MotherQuestionHandler extends QuestionHandler {
private bool canHandle(String question) {
return question.startsWith("Who") && question.endsWith("Mother");
}
public void handle(String question) {
if( canHandle(question) ) {
String mother = "..."; //name
System.out.println(mother);
} else {
super.successor.handle(question);
}
}
}
the final handler, when question cannot be handled:
public class UnhandledQuestionHandler extends QuestionHandler {
public void handle(String question) {
throw new UnhandledQuestionException("question not recognized");
}
}
you should create
UnhandledQuestionException
first, that extends Exception class.
you should create QuestionHandlerFactory too.
public class QuestionHandlerFactory {
public static QuestionHandler create() {
//if you can have several variants of this handler combinations, this method shouldn't be static
QuestionHandler healthQuestionHandler = new HealthQuestionHandler();
QuestionHandler motherQuestionHandler = new MotherQuestionHandler();
QuestionHandler unhandledQuestionHandler = new UnhandledQuestionHandler()'
motherQuestionHandler.setSuccessor(unhandledQuestionHandler);
healthQuestionHandler.setSuccessor(motherQuestionHandler);
return healthQuestionHandler;
}
}
and in the user of this class will be:
QuestionHandler handler = QuestionHandlerFactory.create();
try {
handler.handle(question);
} catch( UnhandledQuestionException ex ) {
System.out.println(ex.getMessage());
}

create an enum for your Constants such "WHO","HOW", .... and WHERE" then try to use switch after that
you can create enum in the same class

You can use Factory pattern and a strategy pattern. Since Qestion is being asked in a different class (let's call it QueryResolver ) it should look like this :
class QueryProcessor
{
private IQueryResolver _ resolver;
//We will be injecting our dependencies in the constructor (Dependency Inversion)
public QueryProcessor(IQueryResolver resolver )
{
_resolver = resolver;
}
public string ProcessQuery()
{
_resolver.ResolveQuery();
}
Now your QueryResolver Implements the IQueryResolver interface
public interface IQueryResover
{
string ResolveQuery();
}
And you will have multiple implementation of IQueryResolver each responsible for a particular kind of Query e.g.:
//This particular implementation know how to resolve question including the "Who" key word.
class WhoQueryResolver : IQueryResolver
{
private string _question;
public WhoQueryResolver(string question)
{
_question = question;
}
public string ResolveQuery()
{
//do a lot of things here.
System.out.print(getParents().getMother());
}
Similarly,
class HowQueryResolver : IQueryResolver
{
private string _question;
public HowQueryResolver(string question)
{
_question = question;
}
public string ResolveQuery()
{
//do a lot of things here.
System.out.print(GetActualHealth());
}
than finally a factory which return concrete implementation of IQueryResolver
public class QueryResolverFactory
{
public static IQueryResolver GetQueryResolver()
{
if (question.startsWith("How") && question.endsWith("Josh?"))
{
return new HowQueryResolver(question);
}
else if (question.startsWith("Who") && question.endsWith("mother?"))
{
return new WhoQueryResolver(question);
}
}
}