Merge pull request #1231 from c-thornton/prime-factors

prime-factors: added hints about no starter implementation

exercises/prime-factors/.meta/hints.md

@@ -0,0 +1,58 @@
+Since this exercise has difficulty 5 it doesn't come with any starter implementation.
+This is so that you get to practice creating classes and methods which is an important part of programming in Java.
+It does mean that when you first try to run the tests, they won't compile.
+They will give you an error similar to:
+```
+ path-to-exercism-dir\exercism\java\name-of-exercise\src\test\java\ExerciseClassNameTest.java:14: error: cannot find symbol
+        ExerciseClassName exerciseClassName = new ExerciseClassName();
+        ^
+ symbol:   class ExerciseClassName
+ location: class ExerciseClassNameTest
+```
+This error occurs because the test refers to a class that hasn't been created yet (`ExerciseClassName`).
+To resolve the error you need to add a file matching the class name in the error to the `src/main/java` directory.
+For example, for the error above you would add a file called `ExerciseClassName.java`.
+
+When you try to run the tests again you will get slightly different errors.
+You might get an error similar to:
+```
+  constructor ExerciseClassName in class ExerciseClassName cannot be applied to given types;
+        ExerciseClassName exerciseClassName = new ExerciseClassName("some argument");
+                                              ^
+  required: no arguments
+  found: String
+  reason: actual and formal argument lists differ in length
+```
+This error means that you need to add a [constructor](https://docs.oracle.com/javase/tutorial/java/javaOO/constructors.html) to your new class.
+If you don't add a constructor, Java will add a default one for you.
+This default constructor takes no arguments.
+So if the tests expect your class to have a constructor which takes arguments, then you need to create this constructor yourself.
+In the example above you could add:
+```
+ExerciseClassName(String input) {
+
+}
+``` 
+That should make the error go away, though you might need to add some more code to your constructor to make the test pass!
+
+You might also get an error similar to:
+```
+  error: cannot find symbol
+        assertEquals(expectedOutput, exerciseClassName.someMethod());
+                                                       ^
+  symbol:   method someMethod()
+  location: variable exerciseClassName of type ExerciseClassName
+```
+This error means that you need to add a method called `someMethod` to your new class.
+In the example above you would add:
+```
+String someMethod() {
+  return "";
+}
+```
+Make sure the return type matches what the test is expecting.
+You can find out which return type it should have by looking at the type of object it's being compared to in the tests.
+Or you could set your method to return some random type (e.g. `void`), and run the tests again.
+The new error should tell you which type it's expecting.
+
+After having resolved these errors you should be ready to start making the tests pass!

exercises/prime-factors/README.md

@@ -29,6 +29,68 @@ You can check this yourself:
 - = 60
 - Success!
 
+# Java Tips
+
+Since this exercise has difficulty 5 it doesn't come with any starter implementation.
+This is so that you get to practice creating classes and methods which is an important part of programming in Java.
+It does mean that when you first try to run the tests, they won't compile.
+They will give you an error similar to:
+```
+ path-to-exercism-dir\exercism\java\name-of-exercise\src\test\java\ExerciseClassNameTest.java:14: error: cannot find symbol
+        ExerciseClassName exerciseClassName = new ExerciseClassName();
+        ^
+ symbol:   class ExerciseClassName
+ location: class ExerciseClassNameTest
+```
+This error occurs because the test refers to a class that hasn't been created yet (`ExerciseClassName`).
+To resolve the error you need to add a file matching the class name in the error to the `src/main/java` directory.
+For example, for the error above you would add a file called `ExerciseClassName.java`.
+
+When you try to run the tests again you will get slightly different errors.
+You might get an error similar to:
+```
+  constructor ExerciseClassName in class ExerciseClassName cannot be applied to given types;
+        ExerciseClassName exerciseClassName = new ExerciseClassName("some argument");
+                                              ^
+  required: no arguments
+  found: String
+  reason: actual and formal argument lists differ in length
+```
+This error means that you need to add a [constructor](https://docs.oracle.com/javase/tutorial/java/javaOO/constructors.html) to your new class.
+If you don't add a constructor, Java will add a default one for you.
+This default constructor takes no arguments.
+So if the tests expect your class to have a constructor which takes arguments, then you need to create this constructor yourself.
+In the example above you could add:
+```
+ExerciseClassName(String input) {
+
+}
+``` 
+That should make the error go away, though you might need to add some more code to your constructor to make the test pass!
+
+You might also get an error similar to:
+```
+  error: cannot find symbol
+        assertEquals(expectedOutput, exerciseClassName.someMethod());
+                                                       ^
+  symbol:   method someMethod()
+  location: variable exerciseClassName of type ExerciseClassName
+```
+This error means that you need to add a method called `someMethod` to your new class.
+In the example above you would add:
+```
+String someMethod() {
+  return "";
+}
+```
+Make sure the return type matches what the test is expecting.
+You can find out which return type it should have by looking at the type of object it's being compared to in the tests.
+Or you could set your method to return some random type (e.g. `void`), and run the tests again.
+The new error should tell you which type it's expecting.
+
+After having resolved these errors you should be ready to start making the tests pass!
+
+
 # Running the tests
 
 You can run all the tests for an exercise by entering