My current problem is that I am assigned to created a program that should within the private fields assign tasks[] an array of task. Then within the constructor, that creates the task[] array, giving it the capacity of INITIAL_CAPAITY, and setting numTasks to zero.
I am new and confused on I can tackle this problem
I have tried declaring it within the constructor but there has been no luck.
Task.java
public class Task {
private String name;
private int priority;
private int estMinsToComplete;
public Task(String name, int priority, int estMinsToComplete) {
this.name=name;
this.priority=priority;
this.estMinsToComplete = estMinsToComplete;
}
public String getName() {
return name;
}
public int getPriority() {
return priority;
}
public int getEstMinsToComplete() {
return estMinsToComplete;
}
public void setName(String name) {
this.name = name;
}
public void setEstMinsToComplete(int newestMinsToComplete) {
this.estMinsToComplete = newestMinsToComplete;
}
public String toString() {
return name+","+priority+","+estMinsToComplete;
}
public void increasePriority(int amount) {
if(amount>0) {
this.priority+=amount;
}
}
public void decreasePriority(int amount) {
if (amount>priority) {
this.priority=0;
}
else {
this.priority-=amount;
}
}
}
HoneyDoList.java
public class HoneyDoList extends Task{
private String[] tasks;
//this issue to my knowledge is the line of code above this
private int numTasks;
private int INITIAL_CAPACITY = 5;
public HoneyDoList(String tasks, int numTasks, int INITIAL_CAPACITY,int estMinsToComplete, String name,int priority) {
super(name,priority,estMinsToComplete);
numTasks = 0;
tasks = new String[]{name,priority,estMinsToComplete};
//as well as here^^^^^^^^
}
My expected result is to be able to print out the list through honeydo class. I need to manipulate the code a bit more after adding a few other methods.
Your problem is that your constructor parameter tasks has the same name as that field of your class.
So you assign to the method parameter in your constructor, not to the field. And luckily those two different "tasks" entities have different types, otherwise you would not even notice that something is wrong.
Solution: use
this.tasks = new String...
within the body of the constructor!
And the real answer: you have to pay a lot attention to such subtle details. And by using different names for different things you avoid a whole class of issues!
Also note: it sounds a bit strange that a class named Task contains a list of tasks, which are then strings. The overall design is a bit weird...
I want to define a default value for an Enum class. The idea of my enum is to define a few specific String values and tie them to enumerations. However, if a user provide an String that I am not expecting, I want the enum to reflect an invalid state. Consider
public class EnumDemo {
public enum Food {
HAMBURGER("h"), FRIES("f"), HOTDOG("d"), ARTICHOKE("a"), INVALID("invalid");
Food(String code) {
this.code = code;
}
private final String code;
public String getCode() {
return code;
}
public static Food fromString(String value) {
return Arrays.stream(Food.values()).filter(s -> s.code.equalsIgnoreCase(value)).findFirst()
.orElse(Food.INVALID);
}
}
public static void main(String[] args) {
Food f1 = Food.fromString("h");
System.out.println(f1 + " " + f1.getCode());
f1 = Food.fromString("x");
System.out.println(f1 + " " + f1.getCode());
}
}
this prints out
HAMBURGER h
INVALID invalid
The problem here is that I am defining the string for the code. invalid is hardcoded as per
INVALID("invalid")
Is it possible to make this a variable? So that I can keep track of what the invalid input was? I tried
INVALID(String x)
but obviously got a syntax exception. Would it just be better not to use an enum?
Lastly, the reason I want to keep track of invalid inputs is that in the future, I want the flexibility to change the enum depending on the users.
You could create a wrapper to stash the original input:
public class FoodInput {
private final Food food;
private final String input;
public FoodInput(String input) {
this.food = Food.fromString(input);
this.input = input;
}
public Food getFood() {
return food;
}
public String getInput() {
return input;
}
}
My Enum type ProductType is properly saving to XML but it doesn't want to unmarshal when opening the file.
I made EnumAdapter:
public class EnumAdapter extends XmlAdapter<String, ProductType>
{
#Override
public ProductType unmarshal(String value) throws Exception {
try {
return ProductType.valueOf(value);
}
catch(Exception e) {
throw new JAXBException(e);
}
}
#Override
public String marshal(ProductType value) {
return value.toString();
}
}
My Product class:
public class Product {
private final IntegerProperty ilosc; //quantity
private final StringProperty nazwa; //name
private final ObjectProperty<ProductType> typ; //type
private final BooleanProperty dostepnosc;
public Product()
{
this(null, 0, ProductType.ALKOHOL, true);
}
public Product(String nazwa, int ilosc, ProductType typ, boolean dostepnosc) {
this.nazwa = new SimpleStringProperty(nazwa);
this.ilosc = new SimpleIntegerProperty(ilosc);
this.typ = new SimpleObjectProperty<>(typ);
this.dostepnosc = new SimpleBooleanProperty(dostepnosc);
}
.
.
.
#XmlJavaTypeAdapter(EnumAdapter.class)
public ProductType getTyp() {
return typ.get();
}
After opening the XML in my app enum is always setting to the value from default constructor (which is ALCOHOL, if I change it, enum is setting to whatever it is). I also know that marshalling from EnumAdapter works properly, I can change it to whatever I want. Please help.
I solved it, I was missing proper setting function:
public void setTyp(ProductType type){
this.typ.setValue(type);
This question already has answers here:
How to retrieve Enum name using the id?
(11 answers)
Closed 9 years ago.
I need to do look up in an enum by an int . The enum is as folows :
public enum ErrorCode{
MissingReturn(1,"Some long String here"),
InvalidArgument(2,"Another long String here");
private final int shortCode ;
private final String detailMessage;
ErrorCode(shortCode ,detailMessage){
this.shortCode = shortCode ;
this.detailMessage= detailMessage;
}
public String getDetailedMessage(){
return this.detailMessage;
}
public int getShortCode(){
return this.shortCode ;
}
}
Now Is need to have a lookup method that would take an int code and should return me the String message pertaining to that code that is stored in the Enum.Passing a "1" should return me the String "Some long String here". What is the best way to implement this functionality?
public static String lookUpMessageFromCode(int code){
}
P.S: Is the class EnumMap useful for this kind of use case? If yes,please let me know why?
Depending on the int values that you associated with your enum, I would add a static array of ErrorCodes, or a static Map<Integer,ErrorCode> to your enum class, and use it to do a lookup in the message from code method. In your case, an array is more appropriate, because you have values 1 and 2 which are small. I would also change the signature to return ErrorCode.
private static final ErrorCode[] allErrorCodes = new ErrorCode[] {
null, MissingReturn, InvalidArgument
};
public static ErrorCode lookUpByCode(int code) {
// Add range checking to see if the code is valid
return allErrorCodes[code];
}
The callers who need the message would obtain it like this:
String message = ErrorCode.lookUpByCode(myErrorCode).getDetailedMessage();
I would simply iterate through your Enum values and check the code. This solution lets you utilize the existing Enum with out creating another object to manage.
public enum ErrorCode {
MissingReturn(1, "Some long String here"),
InvalidArgument(2, "Another long String here");
private final int shortCode;
private final String detailMessage;
ErrorCode(int shortCode, String detailMessage) {
this.shortCode = shortCode;
this.detailMessage = detailMessage;
}
public String getDetailedMessage() {
return this.detailMessage;
}
public int getShortCode() {
return this.shortCode;
}
public static String lookUpMessageFromCode(int code) {
String message = null;
for (ErrorCode errorCode : ErrorCode.values()) {
if (errorCode.getShortCode() == code) {
message = errorCode.getDetailedMessage();
break;
}
}
return message;
}
public static void main(String[] args) {
System.out.println(ErrorCode.lookUpMessageFromCode(1));
System.out.println(ErrorCode.lookUpMessageFromCode(2));
}
}
One thing to note
The Enum constructor is missing the type information regarding its parameters.
ErrorCode(int shortCode, String detailMessage) {
this.shortCode = shortCode;
this.detailMessage = detailMessage;
}
Here is another option:
public static String lookUpMessageFromCode(int code){
for(ErrorCode ec:ErrorCode.values()){
if(ec.shortCode==code)
return ec.detailMessage;
}
return null;
}
I would like to lookup an enum from its string value (or possibly any other value). I've tried the following code but it doesn't allow static in initialisers. Is there a simple way?
public enum Verbosity {
BRIEF, NORMAL, FULL;
private static Map<String, Verbosity> stringMap = new HashMap<String, Verbosity>();
private Verbosity() {
stringMap.put(this.toString(), this);
}
public static Verbosity getVerbosity(String key) {
return stringMap.get(key);
}
};
Use the valueOf method which is automatically created for each Enum.
Verbosity.valueOf("BRIEF") == Verbosity.BRIEF
For arbitrary values start with:
public static Verbosity findByAbbr(String abbr){
for(Verbosity v : values()){
if( v.abbr().equals(abbr)){
return v;
}
}
return null;
}
Only move on later to Map implementation if your profiler tells you to.
I know it's iterating over all the values, but with only 3 enum values it's hardly worth any other effort, in fact unless you have a lot of values I wouldn't bother with a Map it'll be fast enough.
You're close. For arbitrary values, try something like the following:
public enum Day {
MONDAY("M"), TUESDAY("T"), WEDNESDAY("W"),
THURSDAY("R"), FRIDAY("F"), SATURDAY("Sa"), SUNDAY("Su"), ;
private final String abbreviation;
// Reverse-lookup map for getting a day from an abbreviation
private static final Map<String, Day> lookup = new HashMap<String, Day>();
static {
for (Day d : Day.values()) {
lookup.put(d.getAbbreviation(), d);
}
}
private Day(String abbreviation) {
this.abbreviation = abbreviation;
}
public String getAbbreviation() {
return abbreviation;
}
public static Day get(String abbreviation) {
return lookup.get(abbreviation);
}
}
with Java 8 you can achieve with this way:
public static Verbosity findByAbbr(final String abbr){
return Arrays.stream(values()).filter(value -> value.abbr().equals(abbr)).findFirst().orElse(null);
}
#Lyle's answer is rather dangerous and I have seen it not work particularly if you make the enum a static inner class. Instead I have used something like this which will load the BootstrapSingleton maps before the enums.
Edit this should not be a problem any more with modern JVMs (JVM 1.6 or greater) but I do think there are still issues with JRebel but I haven't had a chance to retest it.
Load me first:
public final class BootstrapSingleton {
// Reverse-lookup map for getting a day from an abbreviation
public static final Map<String, Day> lookup = new HashMap<String, Day>();
}
Now load it in the enum constructor:
public enum Day {
MONDAY("M"), TUESDAY("T"), WEDNESDAY("W"),
THURSDAY("R"), FRIDAY("F"), SATURDAY("Sa"), SUNDAY("Su"), ;
private final String abbreviation;
private Day(String abbreviation) {
this.abbreviation = abbreviation;
BootstrapSingleton.lookup.put(abbreviation, this);
}
public String getAbbreviation() {
return abbreviation;
}
public static Day get(String abbreviation) {
return lookup.get(abbreviation);
}
}
If you have an inner enum you can just define the Map above the enum definition and that (in theory) should get loaded before.
And you can't use valueOf()?
Edit: Btw, there is nothing stopping you from using static { } in an enum.
In case it helps others, the option I prefer, which is not listed here, uses Guava's Maps functionality:
public enum Vebosity {
BRIEF("BRIEF"),
NORMAL("NORMAL"),
FULL("FULL");
private String value;
private Verbosity(final String value) {
this.value = value;
}
public String getValue() {
return this.value;
}
private static ImmutableMap<String, Verbosity> reverseLookup =
Maps.uniqueIndex(Arrays.asList(Verbosity.values()), Verbosity::getValue);
public static Verbosity fromString(final String id) {
return reverseLookup.getOrDefault(id, NORMAL);
}
}
With the default you can use null, you can throw IllegalArgumentException or your fromString could return an Optional, whatever behavior you prefer.
since java 8 you can initialize the map in a single line and without static block
private static Map<String, Verbosity> stringMap = Arrays.stream(values())
.collect(Collectors.toMap(Enum::toString, Function.identity()));
public enum EnumRole {
ROLE_ANONYMOUS_USER_ROLE ("anonymous user role"),
ROLE_INTERNAL ("internal role");
private String roleName;
public String getRoleName() {
return roleName;
}
EnumRole(String roleName) {
this.roleName = roleName;
}
public static final EnumRole getByValue(String value){
return Arrays.stream(EnumRole.values()).filter(enumRole -> enumRole.roleName.equals(value)).findFirst().orElse(ROLE_ANONYMOUS_USER_ROLE);
}
public static void main(String[] args) {
System.out.println(getByValue("internal role").roleName);
}
}
Perhaps, take a look at this. Its working for me.
The purpose of this is to lookup 'RED' with '/red_color'.
Declaring a static map and loading the enums into it only once would bring some performance benefits if the enums are many.
public class Mapper {
public enum Maps {
COLOR_RED("/red_color", "RED");
private final String code;
private final String description;
private static Map<String, String> mMap;
private Maps(String code, String description) {
this.code = code;
this.description = description;
}
public String getCode() {
return name();
}
public String getDescription() {
return description;
}
public String getName() {
return name();
}
public static String getColorName(String uri) {
if (mMap == null) {
initializeMapping();
}
if (mMap.containsKey(uri)) {
return mMap.get(uri);
}
return null;
}
private static void initializeMapping() {
mMap = new HashMap<String, String>();
for (Maps s : Maps.values()) {
mMap.put(s.code, s.description);
}
}
}
}
Please put in your opinons.
If you want a default value and don't want to build lookup maps, you can create a static method to handle that.
This example also handles lookups where the expected name would start with a number.
public static final Verbosity lookup(String name) {
return lookup(name, null);
}
public static final Verbosity lookup(String name, Verbosity dflt) {
if (StringUtils.isBlank(name)) {
return dflt;
}
if (name.matches("^\\d.*")) {
name = "_"+name;
}
try {
return Verbosity.valueOf(name);
} catch (IllegalArgumentException e) {
return dflt;
}
}
If you need it on a secondary value, you would just build the lookup map first like in some of the other answers.
You can define your Enum as following code :
public enum Verbosity
{
BRIEF, NORMAL, FULL, ACTION_NOT_VALID;
private int value;
public int getValue()
{
return this.value;
}
public static final Verbosity getVerbosityByValue(int value)
{
for(Verbosity verbosity : Verbosity.values())
{
if(verbosity.getValue() == value)
return verbosity ;
}
return ACTION_NOT_VALID;
}
#Override
public String toString()
{
return ((Integer)this.getValue()).toString();
}
};
See following link for more clarification
You can use the Enum::valueOf() function as suggested by Gareth Davis & Brad Mace above, but make sure you handle the IllegalArgumentException that would be thrown if the string used is not present in the enum.