I have defined my own expection class:
public class ProduktException extends Exception {
public ProduktException(String msg){
//null
}
public static void throwProduktNotCreatedException() throws ProduktException {
throw new ProduktException("Cannot be created!");
}
public static void throwProduktNotDeletedException () throws ProduktException {
throw new ProduktException("Cannot be deleted!");
}
}
My Problem is I do not know how to throw them when I try:
try {
...
} catch(ProduktNotDeletedException e) {
e.toString();
}
That does not work... But I want to have these structure! What is wrong?
I appreaciate your answer!!!
UPDATE:
My Problem is, I do not want to create several Exception Klasses I want to have all Exceptions in one class. Is there possibly a solution for that?
If you need to differentiate between different kinds of exceptions, just create 2 different exceptions, maybe something like:
public class ProduktException extends Exception
{
public ProduktException(String msg){
//null
}
}
Then have:
public class ProduktNotDeletedException extends ProduktException
{
....
}
and
public class ProduktNotCreatedException extends ProduktException
{
....
}
Then you can catch one or the other, or both.
try {
...
} catch(ProduktNotDeletedException e1) {
e1.toString();
} catch(ProduktNotCreatedException e2) {
e2.toString();
}
EDIT:
For a single class what I mean is:
public class ProduktException extends Exception {
boolean notDeleted;
boolean notCreated;
public ProduktException(String msg){
super(msg);
}
public boolean isNotDeleted() {
return(notDeleted);
}
public boolean isNotCreated() {
return(notCreated);
}
public static void throwProduktNotCreatedException() throws ProduktException {
ProduktException e = new ProduktException("Cannot be created!");
e.notCreated = true;
throw e;
}
public static void throwProduktNotDeletedException () throws ProduktException {
ProduktException e = new ProduktException("Cannot be deleted!");
e.notDeleted = true;
throw e;
}
}
Then in your try/catch:
try {
...
} catch(ProduktException e) {
e.toString();
if(e.isNotCreated()) {
// do something
}
if(e.isNotDeleted()) {
// do something
}
}
You need to either catch ProduktException, e.g.
try {
...
} catch (ProduktException e) {
e.toString();
}
or declare subtypes, e.g.
public ProduktNotDeletedException extends ProduktException
You'll probably want to pass the message in the constructor up, so add the following in your constructor:
super(msg);
The Syntax given below.
class RangeException extends Exception
{
String msg;
RangeException()
{
msg = new String("Enter a number between 10 and 100");
}
}
public class MyCustomException
{
public static void main (String args [])
{
try
{
int x = 1;
if (x < 10 || x >100) throw new RangeException();
}
catch(RangeException e)
{
System.out.println (e);
}
}
}
What you could do if you don't want to create multiple subclasses of your ProduktException for each different type of exception you need to throw is to include a code in the exception which will let you know what is wrong. Something like this:
public class ProduktException extends Exception {
private Code exceptionCode;
private String message
public ProduktException(Code code, String msg){
this.message = msg;
this.exceptionCode = code;
}
//Getters and setters for exceptionCode and message
}
Code can be an enum so that your application can know that each code corresponds to a specific "problem" (product not created, product not deleted, etc.). You can then throw your exceptions like this
throw new ProduktException(Code.PRODUCT_NOT_CREATED,
"Error while creating product");
And when you catch it you can differentiate based on the code.
catch (ProduktException ex) {
if (ex.getExceptionCode().equals(Code.PRODUCT_NOT_CREATED)) {
...
}
else {
...
}
}
Related
New to this topic and right now I'm stuck at a brick wall. I have 2 classes, parent class: Controller.java and subclass: GreenhouseControls.java. I need to serialize a GreenhouseControls object but also an instance variable (eventList) from its superclass Controller.java.
My serialization happens when an inner class of GreenhouseControls.java throws a custom ControllerException, which is caught in the main method. Before terminating the program, the GreenhouseControls object should be saved (including the field from its superclass).
Why is a NotSerializableException thrown by the inner class WindowMalfunction of GreenhouseControls? Anyone have any ideas, as I am seriously stuck?
What I tried is the following:
Implement serializable on Controller.java. This is because if the superclass is serializable, then subclass is automatically serializable, however this throws java.io.NotSerializableException: GreenhouseControls$WindowMalfunction, (WindowMalfunction is the inner class that throws the initial exception to begin the serialization processs).
Implement serializable on GreenhouseControls.java and implement custom serialization by overriding writeObject() and readObject() to save the field from the superclass. This approach yet again throws the same exception as the approach 1.
private void writeObject(ObjectOutputStream out) throws IOException {
out.defaultWriteObject();
out.writeObject(super.eventList);
}
private void readObject(ObjectInputStream in) throws IOException,
ClassNotFoundException {
in.defaultReadObject();
Object obj = in.readObject();
List<Event> x = cast(obj);
super.eventList = x;
}
Controller.java
import java.io.*;
import java.text.SimpleDateFormat;
import java.util.*;
public class Controller {
// THIS IS THE VARIABLE I NEED TO SAVE
protected List<Event> eventList = new ArrayList<Event>();
public void addEvent(Event c) {
eventList.add(c);
}
public void run() throws ControllerException {
while (eventList.size() > 0)
// Make a copy so you're not modifying the list
// while you're selecting the elements in it:
for (Event e : new ArrayList<Event>(eventList))
if (e.ready()) {
System.out.println(e);
e.action();
eventList.remove(e);
}
}
public static void shutDown() { }
}
GreenhouseControls.java class (note I have removed the inner classes and other code from it and only left related info)
public class GreenhouseControls extends Controller implements Serializable {
private int errorcode = 0;
public class WindowMalfunction extends Event {
public WindowMalfunction(long delayTime) {
super(delayTime);
}
public void action() throws ControllerException {
windowok = false;
throw new ControllerException("Window malfunction");
}
public String toString() {
return "Window malfunction";
}
}
public class PowerOut extends Event {
public PowerOut(long delayTime) {
super(delayTime);
}
public void action() throws ControllerException {
poweron = false;
throw new ControllerException("Power out");
}
public String toString() {
return "Power out";
}
}
// Various other inner classes that extend event exist
public static void serializeObject(GreenhouseControls gc) {
FileOutputStream fileOut;
ObjectOutputStream out;
try {
fileOut = new FileOutputStream("dump.out");
out = new ObjectOutputStream(fileOut);
out.writeObject(gc);
System.out.println("WERRROR code: " + gc.getError());
out.close();
fileOut.close();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
private void writeObject(ObjectOutputStream out) throws IOException {
out.defaultWriteObject();
out.writeObject(super.eventList);
}
private void readObject(ObjectInputStream in) throws IOException,
ClassNotFoundException {
in.defaultReadObject();
Object obj = in.readObject();
List<Event> x = cast(obj);
super.eventList = x;
}
#SuppressWarnings("unchecked")
public static <T extends List<?>> T cast(Object obj) {
return (T) obj;
}
public int getError() {
return errorcode;
}
public Fixable getFixable(int errorcode) {
switch (errorcode) {
case 1:
return new FixWindow();
case 2:
return new PowerOn();
default:
return null;
}
}
public static void main(String[] args) {
GreenhouseControls gc = null;
try {
String option = args[0];
String filename = args[1];
if (!(option.equals("-f")) && !(option.equals("-d"))) {
System.out.println("Invalid option");
printUsage();
}
// gc = new GreenhouseControls();
if (option.equals("-f")) {
gc = new GreenhouseControls();
gc.addEvent(gc.new Restart(0, filename));
}
gc.run();
} catch (ArrayIndexOutOfBoundsException e) {
System.out.println("Invalid number of parameters");
printUsage();
} catch (ControllerException e) {
String errormsg;
if (e.getMessage().equals("Window malfunction")) {
gc.errorcode = 1;
errormsg = "Window malfunction event occurred Error code: " + gc.errorcode;
} else {
gc.errorcode = 2;
errormsg = "Power out event occurred Error code: " + gc.errorcode;
}
logError(errormsg);
serializeObject(gc);
gc.displayEventList();
shutDown();
}
}
}
Event.java
public abstract class Event {
private long eventTime;
protected final long delayTime;
public Event(long delayTime) {
this.delayTime = delayTime;
start();
}
public void start() { // Allows restarting
eventTime = System.currentTimeMillis() + delayTime;
}
public boolean ready() {
return System.currentTimeMillis() >= eventTime;
}
public abstract void action() throws ControllerException;
Event has to be Serializable too.
Change
public abstract class Event {
to
public abstract class Event implements Serializable {
I would like to generalize the following pattern:
setChangeListener = c -> {
try {
// do something dangerous
} catch (final IOException e) {
logger.error(e.getLocalizedMessage(), e);
}
};
I would like to use it like this:
errorLoggingSetChangeListener = c -> {
// do something dangerous
};
I was thinking about this:
public class ErrorLoggingSetChangeListener<T> implements SetChangeListener<T> {
private static final Logger logger = Logger.getLogger(ErrorLoggingSetChangeListener.class);
private final SetChangeListener<T> delegate;
#Override
public void onChanged(final SetChangeListener.Change<? extends T> change) {
try {
delegate.onChanged(change);
} catch (final Exception e) {
if (logger.isEnabledFor(Level.ERROR)) {
logger.error(e.getLocalizedMessage(), e);
}
}
}
public ErrorLoggingSetChangeListener(final SetChangeListener<T> delegate) {
super();
this.delegate = delegate;
}
}
But that is not possible, since ErrorLoggingSetChangeListener is not a Functional interface.
Any chance to convert this class to an Functional Interface?
This does not compile:
public interface ErrorLoggingSetChangeListener<T> extends SetChangeListener<T> {
static final Logger logger = Logger.getLogger(ErrorLoggingSetChangeListener.class);
#Override
default void onChanged(final SetChangeListener.Change<? extends T> change) {
try {
SetChangeListener.super.onChanged(change);
} catch (final Exception e) {
if (logger.isEnabledFor(Level.ERROR)) {
logger.error(e.getLocalizedMessage(), e);
}
}
}
}
This does also not compile:
errorLoggingSetChangeListener = new ErrorLoggingSetChangeListener<>(c -> {
throw new IOException();
});
The error message is
Unhandled exception [..]
.
This is similar to #JonnyAW's solution, but combines both classes into a single interface:
import javafx.collections.SetChangeListener;
#FunctionalInterface
public interface ErrorLoggingSetChangeListener<E> extends SetChangeListener<E> {
public void delegate(Change<? extends E> change) throws Exception ;
#Override
public default void onChanged(Change<? extends E> change) {
try {
delegate(change);
} catch (Exception exc) {
// just do a System.out.println here to demo we reach this block:
System.out.println("Custom error handling...");
exc.printStackTrace();
}
}
}
And here's a demo of using this:
import javafx.collections.FXCollections;
import javafx.collections.ObservableSet;
public class Test {
public static void main(String[] args) {
ObservableSet<String> set = FXCollections.observableSet();
ErrorLoggingSetChangeListener<String> listener = c -> {
if (c.wasAdded()) {
int i = Integer.parseInt(c.getElementAdded());
System.out.println("Value added: "+i);
}
};
set.addListener(listener);
set.add("42");
set.add("What do you get when you multiply 6 by 9?");
}
}
which generates the expected output:
Value added: 42
Custom error handling...
java.lang.NumberFormatException: For input string: "What do you get when you multiply 6 by 9?"
at java.lang.NumberFormatException.forInputString(NumberFormatException.java:65)
at java.lang.Integer.parseInt(Integer.java:580)
at java.lang.Integer.parseInt(Integer.java:615)
at Test.lambda$0(Test.java:10)
at ErrorLoggingSetChangeListener.onChanged(ErrorLoggingSetChangeListener.java:12)
at com.sun.javafx.collections.SetListenerHelper$SingleChange.fireValueChangedEvent(SetListenerHelper.java:163)
at com.sun.javafx.collections.SetListenerHelper.fireValueChangedEvent(SetListenerHelper.java:72)
at com.sun.javafx.collections.ObservableSetWrapper.callObservers(ObservableSetWrapper.java:128)
at com.sun.javafx.collections.ObservableSetWrapper.add(ObservableSetWrapper.java:269)
at Test.main(Test.java:17)
here is my implementation, that will compile:
ErrorLoggingSetChangeListener:
import javafx.collections.SetChangeListener;
public class ErrorLoggingSetChangeListener<T> implements SetChangeListener<T> {
private DangerousInterface<T> delegate;
public ErrorLoggingSetChangeListener(DangerousInterface<T> delegate) {
super();
this.delegate = delegate;
}
#Override
public void onChanged(Change<? extends T> change) {
try {
this.delegate.delegate(change);
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
DangerousInterface:
public interface DangerousInterface<T> {
public void delegate(Change<? extends T> change) throws Exception;
}
Main:
SetChangeListener<String> listener = new ErrorLoggingSetChangeListener<>((test) -> {
//no errors here now
throw new Exception();
});
I got definitely no compile errors
EDIT: ok, I got the Problem, you need a new Interface that can actually throw something, now you can wrap it in onChanged
[TL;DR]
The problem is, in AWrapper and AType I have to duplicate pretty much whole function, where there is always the syntax:
public [TYPE/void] METHOD([OPT: args]) throws TestFailedException {
[OPT: TYPE result = null;]
long startTime = System.currentTimeMillis();
while (true) {
try {
beforeOperation();
[OPT: result =] ((WrappedType) element).METHOD([OPT: args]);
handleSuccess();
break;
} catch (Exception e) {
handleSoftFailure(e);
if (System.currentTimeMillis() - startTime > TIMEOUT) {
handleFailure(e);
break;
} else {
try {
Thread.sleep(WAIT_FOR_NEXT_TRY);
} catch (InterruptedException ex) {
}
}
}
}
[OPT: return result;]
}
Lets say I have 2 classes I don't own:
public class IDontOwnThisType {
public void doA(String string) { System.out.println("doA"); }
public String doB(); {System.out.println("doB"); return "doB";}
public OtherTypeIDoNotOwn doC() {System.out.println("doC"); return new OtherTypeIDoNotOwn();}
}
public OtherTypeIDoNotOwn {
public void doD() { System.out.println("doD"); }
public String doE() { System.out.println("doE); }
public OtherTypeIDoNotOwn doF(String string) {System.out.println("doF"); return new OtherTypeIDoNotOwn();}
}
So, I have an interface:
public interface OperationManipulator {
void beforeOperation(); //called before operation
void handleSuccess(); //called after success
void handleSoftFailure(Exception e); //called after every failure in every try
void handleFailure(Exception e) throws TestFailedException; //called after reaching time limit
}
Then interface that extends above one, "mimicking" methods of external classes, but throwing custom exception:
public interface IWrapper<T extends IType> extends OperationManipulator {
public void doA(String string) throws TestFailedException;
public String doB() throws TestFailedException;
public T doC() throws TestFailedException;
}
Then we have IType, which also extends OperationManipulator:
public interface IType<T extends IType> extends OperationManipulator {
public void doD() throws TestFailedException;
public String doE() throws TestFailedException;
public T doF(String string) throws TestFailedException;
}
Then, we have abstract implementations of above interfaces:
public abstract class AType<T extends IType> implements IType{
Object element; // I do not own type of this object, cant modify it.
Class typeClass;
long TIMEOUT = 5000;
long WAIT_FOR_NEXT_TRY = 100;
public AType(Object element) {
this.element = element;
elementClass = this.getClass();
}
/* ... */
}
Then, we override functions from the interfaces, excluding OperationManipulator interface:
Function not returning anything version:
#Override
public void doD() throws TestFailedException {
long startTime = System.currentTimeMillis();
while (true) {
try {
beforeOperation();
((OtherTypeIDoNotOwn) element).doD();
handleSuccess();
break;
} catch (Exception e) {
handleSoftFailure(e);
if (System.currentTimeMillis() - startTime > TIMEOUT) {
handleFailure(e);
break;
} else {
try {
Thread.sleep(WAIT_FOR_NEXT_TRY);
} catch (InterruptedException ex) {
}
}
}
}
Function returning normal reference version:
#Override
public String doE() throws TestFailedException {
String result = null;
long startTime = System.currentTimeMillis();
while (true) {
try {
beforeOperation();
result = ((OtherTypeIDoNotOwn) element).doE();
handleSuccess();
break;
} catch (Exception e) {
handleSoftFailure(e);
if (System.currentTimeMillis() - startTime > TIMEOUT) {
handleFailure(e);
break;
} else {
try {
Thread.sleep(WAIT_FOR_NEXT_TRY);
} catch (InterruptedException ex) {
}
}
}
}
return result;
}
And function returning object of type parameter:
#Override
public T doF(String string) throws TestFailedException {
T result = null;
long startTime = System.currentTimeMillis();
while (true) {
try {
beforeOperation();
OtherTypeIDoNotOwn temp = ((OtherTypeIDoNotOwn) element).doF(string);
result = (T) elementClass.getDeclaredConstructor(Object.class).newInstance(temp);
handleSuccess();
break;
} catch (Exception e) {
handleSoftFailure(e);
if (System.currentTimeMillis() - startTime > TIMEOUT) {
handleFailure(e);
break;
} else {
try {
Thread.sleep(WAIT_FOR_NEXT_TRY);
} catch (InterruptedException ex) {
}
}
}
}
return result;
}
The same goes for AWrapper, but the differences are:
constructor have class argument of stored type
object is cast to IDoNotOwnThisType instead of OtherTypeIDoNotOwn. Functions of this object also may return OtherTypeIDoNotOwn.
IDoNotOwnThisType is type that AWrapper is wrapping.
OtherTypeIDoNotOwn is type that AType is wrapping.
Then, we have implementation of these abstract classes:
public class AssertingType extends AType<AssertingType> {
public AssertingType(Object element) {
super(element);
}
#Override
public void beforeOperation() {
//System.out.println("Asserting type before operation!");
}
#Override
public void handleSuccess() {
//TODO: add to log file and log to output
System.out.println("Asserting type success!");
}
#Override
public void handleFailure(Exception e) throws TestFailedException {
//TODO: add to log file, log to output and throw exception
System.out.println("Asserting type failure!");
e.printStackTrace();
throw new TestFailedException();
}
#Override
public void handleSoftFailure(Exception e) {
//TODO: add to log file, log to output
System.out.println("Asserting type soft failure!");
e.printStackTrace();
}
}
And:
public class AssertingWrapper extends AWrapper<AssertingType> {
public AssertingWrapper (Object driver) {
super(driver, AssertingType.class);
}
#Override
public void beforeOperation() {
//TODO
System.out.println("Asserting wrapper success!");
}
#Override
public void handleSuccess() {
//TODO: add to log file and log to output
System.out.println("Asserting wrapper success!");
}
#Override
public void handleFailure(Exception e) throws TestFailedException {
//TODO: add to log file, log to output and throw exception
System.out.println("Asserting wrapper failure!");
throw new TestFailedException();
}
#Override
public void handleSoftFailure(Exception e) {
//TODO: add to log file, log to output
System.out.println("Asserting wrapper soft failure!");
e.printStackTrace();
}
}
So, we can use it like that:
AssertingWrapper wrapper = new AssertingWrapper(new IDoNotOwnThisType());
AssertingType type = wrapper.doC();
AssertingType type2 = type.doF();
Output:
Asserting wrapper before operation!
doC
Asserting wrapper success!
Asserting type before operation!
doF
Asserting type success!
The full working code is here:
LIVE
The problem is, I have always to write while, try catch etc in AType and AWrapper, can I somehow reduce code duplication? In the example i provided just 3 functions per class, but in my real code I have 50+ methods. Can I somehow wrap these functions so thepart that is repeating is not duplicated?
Your problem appears to be quite complicated, and I cannot claim to have been able to successfully wrap my mind around it, but I will give it a try, because it appears to be a very interesting problem and because I happen to have some experience in dealing with situations that yours appears similar to.
Please excuse me if my answer turns out to be completely off the mark due to a misunderstanding on my part.
So, what it appears that you are looking for is a general purpose solution for injecting your own code before and after an invocation where the invocation may be to any method, accepting any number of parameters, and returning any kind of return value.
In java there exists a dynamic proxy facility, which you can find under java.lang.reflect.Proxy.
With it, you can do the following:
ClassLoader classLoader = myInterfaceClass.getClassLoader();
T temp = (T)Proxy.newProxyInstance( classLoader, new Class<?>[] { myInterfaceClass },
invocationHandler );
The invocationHandler is supplied by you, and it is of the following form:
private final InvocationHandler invocationHandler = new InvocationHandler()
{
#Override
public Object invoke( Object proxy, Method method, Object[] arguments )
throws Throwable
{
/* your pre-invocation code goes here */
/* ... */
/* invoke original object */
Object result = method.invoke( myObject, arguments );
/* your post-invocation code goes here */
/* ... */
/* return the result (will probably be null if method was void) */
return result;
}
};
So, I think you might be able to use that to solve your problem with the minimum amount of code.
Neither the creation of a dynamic proxy nor the call to method.invoke() perform terribly well, (you know, reflection is somewhat slow,) but if you are using it for testing, it should not matter.
I am implementing some elementary sorting algorithms (for the purpose of learning) ,and want to write unittests for them .All the sorting programs have the following common api
...
public static void sort(Comparable[] a);
...
public static boolean isSorted(Comparable[] a);
...
public static boolean isSorted(Comparable[] a),int from ,int to;
...
So,I wrote the following tests for testing the isSorted() method in SelectionSort
public class SelectionSortTests {
String[] a ;
#After
public void tearDown() throws Exception {
a = null;
}
#Test
public void arraySortedSingleElement(){
a = new String[]{"A"};
Assert.assertTrue(SelectionSort.isSorted(a));
}
#Test
public void arraySortedDistinctElements(){
a = new String[]{"A","B","C","D"};
Assert.assertTrue(SelectionSort.isSorted(a));
}
#Test
public void arrayNotSorted(){
a = new String[]{"A","B","C","B"};
Assert.assertFalse(SelectionSort.isSorted(a));
}
...
}
Now I feel that if I were to write tests for say InsertionSort,ShellSort etc ,they would look the same..Only the name of the class under test will change..
So,how should I organize the tests? Is a suite the answer or can I do better using reflection - may be write a driver program to which I can add a list of names of classes to be tested, and the driver invokes runs the common unit tests by passing the classname to it..
I realize this is a common situation..would like to know how this can be handled without spittle or cellotape
UPDATE:
thanks #BevinQ and #Matthew Farwell ,I tried to solve this using Parameterized unit tests.
Used reflection to call the static method ..
Seems to work :) though I think it can still be refactored to avoid duplicate code
#RunWith(Parameterized.class)
public class ParameterizedSortTests {
private Class classToTest;
private Method methodToTest;
public ParameterizedSortTests(String packageName,String classToTest) {
super();
try {
this.classToTest = Class.forName(packageName+"."+classToTest);
} catch (ClassNotFoundException e) {
System.out.println("failed to get class!!");
e.printStackTrace();
}
}
//method return collection of class names to be tested
#Parameterized.Parameters
public static List<Object[]> classesToTest(){
return Arrays.asList(new Object[][]{
{"elemsorts","SelectionSort"} ,
{"elemsorts","InsertionSort"}
});
}
public void setMethod(String method,Class...args){
try {
this.methodToTest = this.classToTest.getMethod(method, args);
} catch (SecurityException e) {
e.printStackTrace();
} catch (NoSuchMethodException e) {
e.printStackTrace();
}
}
#Test
public void arrayIsSorted(){
setMethod("isSorted",Comparable[].class);
String[] a = new String[]{"A","B","C","D"};
Boolean arraySorted = null;
try {
arraySorted = (Boolean)this.methodToTest.invoke(null, new Object[]{a});
System.out.println(this.methodToTest+"returned :"+arraySorted);
} catch (IllegalArgumentException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
} catch (InvocationTargetException e) {
e.printStackTrace();
}
Assert.assertTrue(arraySorted);
}
#Test
public void arrayIsNotSorted(){
setMethod("isSorted",Comparable[].class);
String[] a = new String[]{"A","B","C","B"};
Boolean arraySorted = null;
try {
arraySorted = (Boolean)this.methodToTest.invoke(null, new Object[]{a});
System.out.println(this.methodToTest+"returned :"+arraySorted);
} catch (IllegalArgumentException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
} catch (InvocationTargetException e) {
e.printStackTrace();
}
//System.out.println("arraySorted="+arraySorted);
Assert.assertFalse(arraySorted);
}
}
for interface
public abstract class AbstractSortTests {
String[] a ;
#After
public void tearDown() throws Exception {
a = null;
}
protected abstract Sorter getSorter();
#Test
public void arraySortedSingleElement(){
a = new String[]{"A"};
Assert.assertTrue(getSorter().isSorted(a));
}
#Test
public void arraySortedDistinctElements(){
a = new String[]{"A","B","C","D"};
Assert.assertTrue(getSorter.isSorted(a));
}
...
}
public class SelectionSortTests extends AbstractSortTests {
protected Sorter getSorter(){
return SelectionSort.getInstance();
}
}
public class QuickSortTests extends AbstractSortTests {
protected Sorter getSorter(){
return QuickSort.getInstance();
}
}
using reflection it is a bit messier but still do-able. I have not tested this code so might have
a couple of bugs, but have used this method in the past. Using interfaces would be the preferred method in 99% of cases.
public abstract class AbstractSortTests {
String[] a ;
#After
public void tearDown() throws Exception {
a = null;
}
protected abstract Sorter getSorter();
#Test
public void arraySortedSingleElement() throws Exception{
a = new String[]{"A"};
Assert.assertTrue(executeMethod(getSorterClass(), "isSorted", a);
}
#Test
public void arraySortedDistinctElements() throws Exception{
a = new String[]{"A","B","C","D"};
Assert.assertTrue(executeMethod(getSorterClass(), "isSorted", a);
}
private void executeMethod(Class<?> sortClass, String methodName, String[] values) throws Exception{
return sortClass.getDeclaredMethod(methodName, new Class[]{String[].class}).invoke(null, new Object[]{values});
}
...
}
public class SelectionSortTests extends AbstractSortTests {
protected Class<?> getSorterClass(){
return SelectionSort.class;
}
}
As #BevynQ says, you'll make life a lot easier for yourself if you make your methods non-static, and you implement an interface (called Sorter below). The you can easily use Parameterized. This is a very quick example of how to use it, (untested, uncompiled)
#RunWith(Parameterized.class)
public class SorterTest {
#Parameters
public static Iterable<Object[]> data() {
return Arrays.asList(new Object[][] {
{ new SelectionSort() },
{ new BubbleSort() }
});
}
private final Sorter sorter
public SorterTest(Sorter sorter) {
this.sorter = sorter;
}
#Test
public void arraySortedSingleElement(){
String[] a = new String[]{"A"};
Assert.assertTrue(sorter.isSorted(a));
}
#Test
public void arraySortedDistinctElements(){
String[] a = new String[]{"A","B","C","D"};
Assert.assertTrue(sorter.isSorted(a));
}
#Test
public void arrayNotSorted(){
String[] a = new String[]{"A","B","C","B"};
Assert.assertFalse(sorter.isSorted(a));
}
}
why not something like this?
#Test
public void arraySortedDistinctElements(){
a = new String[]{"A","B","C","D"};
Assert.assertTrue(SelectionSort.isSorted(a));
Assert.assertTrue(InsertionSort.isSorted(a));
Assert.assertTrue(QuickSort.isSorted(a));
}
I don't think you have more than 10 different sortings to test. so it should be good.
otherway, you can declare all Sorting classes in Array and load using Class properties.
I am working on some workflow and it is possible to raise many exceptions in that. I heard that we can keep all those possible exceptions in an Enum (Exception1, Exception2 ...) and use it. How can we do that using Enums in Java?
You can add the classes of exceptions with
enum EnumWithExceptions {
ENUM1(Exception1.class, Exception2.class),
ENUM2(Exception3.class);
private final Class<? extends Exception>[] exceptions;
private EnumWithExceptions(Class<? extends Exception>... exceptions) {
this.exceptions = exceptions;
}
public boolean matches(Exception e) {
for(Class<? extends Exception> e2: exceptions)
if (e2.isInstance(e)) return true;
return false;
}
}
} catch(Exception e){
if (ENUM1.matches(e)){
//do something
} else if(ENUM2.matches(e)) {
//do something
} else {
//do something
}
}
enum Fred {
SAM(AnException.class),
I(AnotherException.class),
AM(YetAnotherException.class)
;
private Throwable t;
Fred(Throwable throwable) {
this.t = throwable;
}
public Throwable getThrowable() {
return t;
}
}
...
throw Fred.SAM.getThrowable();
Why not store the exceptions in an ArrayList? Or if you want to name the index, you could use a HashMap.
import java.util.ArrayList;
import java.util.HashMap;
public final class ExceptionStorage {
private static int exceptionCount = 0;
private static HashMap<String, Exception> indexedExceptions = new HashMap<>();
private static ArrayList<Exception> exceptions = new ArrayList();
public static void addException(Exception e) {
exceptions.add(e);
}
public static void putException(Exception e) {
indexedExceptions.put("Exception" + (++exceptionCount), e);
}
public static ArrayList<Exception> getUnindexedExceptions() {
return this.exceptions;
}
public static HashMap<String, Exception> getIndexedExceptions() {
return this.indexedExceptions;
}
}
Obviously you would have to modify the code to use either ArrayList or HashMap, but I think this would be a better solution than using Enums.