Best way to create enum of strings?

Best way to create enum of strings? - java

What is the best way to have a enum type represent a set of strings?
I tried this:
enum Strings{
STRING_ONE("ONE"), STRING_TWO("TWO")
}
How can I then use them as Strings?

I don't know what you want to do, but this is how I actually translated your example code....
package test;
/**
* #author The Elite Gentleman
*
*/
public enum Strings {
STRING_ONE("ONE"),
STRING_TWO("TWO")
;
private final String text;
/**
* #param text
*/
Strings(final String text) {
this.text = text;
}
/* (non-Javadoc)
* #see java.lang.Enum#toString()
*/
#Override
public String toString() {
return text;
}
}
Alternatively, you can create a getter method for text.
You can now do Strings.STRING_ONE.toString();

Custom String Values for Enum
from http://javahowto.blogspot.com/2006/10/custom-string-values-for-enum.html
The default string value for java enum is its face value, or the element name. However, you can customize the string value by overriding toString() method. For example,
public enum MyType {
ONE {
public String toString() {
return "this is one";
}
},
TWO {
public String toString() {
return "this is two";
}
}
}
Running the following test code will produce this:
public class EnumTest {
public static void main(String[] args) {
System.out.println(MyType.ONE);
System.out.println(MyType.TWO);
}
}
this is one
this is two

Use its name() method:
public class Main {
public static void main(String[] args) throws Exception {
System.out.println(Strings.ONE.name());
}
}
enum Strings {
ONE, TWO, THREE
}
yields ONE.

Either set the enum name to be the same as the string you want or, more generally,you can associate arbitrary attributes with your enum values:
enum Strings {
STRING_ONE("ONE"), STRING_TWO("TWO");
private final String stringValue;
Strings(final String s) { stringValue = s; }
public String toString() { return stringValue; }
// further methods, attributes, etc.
}
It's important to have the constants at the top, and the methods/attributes at the bottom.

Depending on what you mean by "use them as Strings", you might not want to use an enum here. In most cases, the solution proposed by The Elite Gentleman will allow you to use them through their toString-methods, e.g. in System.out.println(STRING_ONE) or String s = "Hello "+STRING_TWO, but when you really need Strings (e.g. STRING_ONE.toLowerCase()), you might prefer defining them as constants:
public interface Strings{
public static final String STRING_ONE = "ONE";
public static final String STRING_TWO = "TWO";
}

You can use that for string Enum
public enum EnumTest {
NAME_ONE("Name 1"),
NAME_TWO("Name 2");
private final String name;
/**
* #param name
*/
private EnumTest(final String name) {
this.name = name;
}
public String getName() {
return name;
}
}
And call from main method
public class Test {
public static void main (String args[]){
System.out.println(EnumTest.NAME_ONE.getName());
System.out.println(EnumTest.NAME_TWO.getName());
}
}

If you do not want to use constructors, and you want to have a special name for the method, try it this:
public enum MyType {
ONE {
public String getDescription() {
return "this is one";
}
},
TWO {
public String getDescription() {
return "this is two";
}
};
public abstract String getDescription();
}
I suspect that this is the quickest solution. There is no need to use variables final.

Get and set with default values.
public enum Status {
STATUS_A("Status A"), STATUS_B("Status B"),
private String status;
Status(String status) {
this.status = status;
}
public String getStatus() {
return status;
}
}

Related

Object to string delimited format

I have set of objects of different types.
Ex : Employee emp, adress adr
These two classes have list of properties
public class Employee{
private Stringname;
private int age;
}
public class Adress {
private String HouseNo;
private string Street;
private string pin;
}
Each attribute is assigned with some 2 character value
Name (NA), age (AG), HouseNo(HN),Street(ST), pin(PN)
I need to construct a string with these data and delimit with a %
Output:
NA%Vidhya%AG%30%HN%80%ST%1st cross%PN%100100

Each class knows it own data best so I would let each class be responsible for generating the string. As I understand it the two char codes for each field are unique for each class and member and only used when generating the string so only the class would need them.
interface AttributeDescription {
String generateDescription();
}
public class Employee implements AttributeDescription {
//members...
public String generateDescription() {
return String.format(“NA%%%s%%AG%%%d”, name, age)
}
Then simply call this method for all objects implementing the interface.
AttributeDescription object = ...
String attr = object.generateDescription();
I don't think it can be generalized more than this given the requirements.
Update
It might be better to have a builder class for building the string to get a more unified behavior between classes. Here is an example
public class AttributeBuilder {
private builder = new StringBuilder();
public String getAttribute() {
return builder.toString();
}
public void add(String code, String value) {
if (value == null) {
return;
}
builder.append(code);
builder.append(‘%’);
builder.append(value);
builder.append(‘%’);
}
}
And then you would also have to implement add(...) methods for other data types in a similar fashion. The builder could then be used like
public String generateDescription() {
AttributeBuilder builder = new AttributeBuilder();
builder.add(“NA”, name);
builder.add(“AG”, age);
return builder.getAttribute();
}

Executing action depending on enum value

I'm trying to retrieving a value depending on the enum value.
Basically, let's say I have the following enum:
private enum Auth{
KEY, PASSWORD, MAIL;
public String get(){
return "";
}
}
By doing Auth.KEY.get() it would return "mykey", while Auth.MAIL.get() would return "mymail"
I googled a bit but I couldn't find an answer, I didn't try anything before because I totally hadn't an idea on how I could start.

Just add a field and constructor, as explained in the java-docs
Example code:
enum Auth {
KEY("myKey"), PASSWORD("myPass"), MAIL("myMail");
private final String identifier;
Auth(String identifier) {
this.identifier = identifier;
}
public String get(){
return identifier;
}
}
Also note, that there is name() and toString() which may be useful: see also java-enum-why-use-tostring-instead-of-name

Although I strongly advise not to use the following mechanism for getting something simple like a hardcoded String from an enum value and rather use it for associating particular behavior like in java.util.concurrent.TimeUnit, this is how it can be achieved:
private enum Auth {
KEY {
public String get() {
return "mykey";
}
},
PASSWORD {
public String get() {
return "mypassword";
}
},
MAIL {
public String get() {
return "mymail";
}
};
public abstract String get();
}

enum Auth{
private enum Auth{
String value;
KEY("mykey"), PASSWORD("mypassword"), MAIL(mymail");
Auth(String value){
thia.value=value;
}
public String get(){
return value;
}
}

You need to have a string which holds the name of of enum and a constructor which sets it. Then get method returns the name as below.
private enum Auth{
KEY, PASSWORD, MAIL;
string name;
public Auth(string nm) {
name = nm;
}
public String get(){
return name;
}
}

Is there any default method for ENUM? [duplicate]

What is the best way to use the values stored in an Enum as String literals?
For example:
public enum Modes {
some-really-long-string,
mode1,
mode2,
mode3
}
Then later I could use Mode.mode1 to return its string representation as mode1. Without having to keep calling Mode.mode1.toString().

You can't. I think you have FOUR options here. All four offer a solution but with a slightly different approach...
Option One: use the built-in name() on an enum. This is perfectly fine if you don't need any special naming format.
String name = Modes.mode1.name(); // Returns the name of this enum constant, exactly as declared in its enum declaration.
Option Two: add overriding properties to your enums if you want more control
public enum Modes {
mode1 ("Fancy Mode 1"),
mode2 ("Fancy Mode 2"),
mode3 ("Fancy Mode 3");
private final String name;
private Modes(String s) {
name = s;
}
public boolean equalsName(String otherName) {
// (otherName == null) check is not needed because name.equals(null) returns false
return name.equals(otherName);
}
public String toString() {
return this.name;
}
}
Option Three: use static finals instead of enums:
public final class Modes {
public static final String MODE_1 = "Fancy Mode 1";
public static final String MODE_2 = "Fancy Mode 2";
public static final String MODE_3 = "Fancy Mode 3";
private Modes() { }
}
Option Four: interfaces have every field public, static and final:
public interface Modes {
String MODE_1 = "Fancy Mode 1";
String MODE_2 = "Fancy Mode 2";
String MODE_3 = "Fancy Mode 3";
}

Every enum has both a name() and a valueOf(String) method. The former returns the string name of the enum, and the latter gives the enum value whose name is the string. Is this like what you're looking for?
String name = Modes.mode1.name();
Modes mode = Modes.valueOf(name);
There's also a static valueOf(Class, String) on Enum itself, so you could also use:
Modes mode = Enum.valueOf(Modes.class, name);

You could override the toString() method for each enum value.
Example:
public enum Country {
DE {
#Override
public String toString() {
return "Germany";
}
},
IT {
#Override
public String toString() {
return "Italy";
}
},
US {
#Override
public String toString() {
return "United States";
}
}
}
Usage:
public static void main(String[] args) {
System.out.println(Country.DE); // Germany
System.out.println(Country.IT); // Italy
System.out.println(Country.US); // United States
}

As Benny Neugebauer mentions, you could overwrite the toString(). However instead overwriting the toString for each enum field I like more something like this:
public enum Country{
SPAIN("España"),
ITALY("Italia"),
PORTUGAL("Portugal");
private String value;
Country(final String value) {
this.value = value;
}
public String getValue() {
return value;
}
#Override
public String toString() {
return this.getValue();
}
}
You could also add a static method to retrieve all the fields, to print them all, etc.
Simply call getValue to obtain the string associated to each Enum item

mode1.name() or String.valueOf(mode1). It doesn't get better than that, I'm afraid

public enum Modes {
MODE1("Mode1"),
MODE2("Mode2"),
MODE3("Mode3");
private String value;
public String getValue() {
return value;
}
private Modes(String value) {
this.value = value;
}
}
you can make a call like below wherever you want to get the value as a string from the enum.
Modes.MODE1.getvalue();
This will return "Mode1" as a String.

For my enums I don't really like to think of them being allocated with 1 String each. This is how I implement a toString() method on enums.
enum Animal
{
DOG, CAT, BIRD;
public String toString(){
switch (this) {
case DOG: return "Dog";
case CAT: return "Cat";
case BIRD: return "Bird";
}
return null;
}
}

You can use Mode.mode1.name() however you often don't need to do this.
Mode mode =
System.out.println("The mode is "+mode);

As far as I know, the only way to get the name would be
Mode.mode1.name();
If you really need it this way, however, you could do:
public enum Modes {
mode1 ("Mode1"),
mode2 ("Mode2"),
mode3 ("Mode3");
private String name;
private Modes(String s) {
name = s;
}
}

my solution for your problem!
import java.util.HashMap;
import java.util.Map;
public enum MapEnumSample {
Mustang("One of the fastest cars in the world!"),
Mercedes("One of the most beautiful cars in the world!"),
Ferrari("Ferrari or Mercedes, which one is the best?");
private final String description;
private static Map<String, String> enumMap;
private MapEnumSample(String description) {
this.description = description;
}
public String getEnumValue() {
return description;
}
public static String getEnumKey(String name) {
if (enumMap == null) {
initializeMap();
}
return enumMap.get(name);
}
private static Map<String, String> initializeMap() {
enumMap = new HashMap<String, String>();
for (MapEnumSample access : MapEnumSample.values()) {
enumMap.put(access.getEnumValue(), access.toString());
}
return enumMap;
}
public static void main(String[] args) {
// getting value from Description
System.out.println(MapEnumSample.getEnumKey("One of the fastest cars in the world!"));
// getting value from Constant
System.out.println(MapEnumSample.Mustang.getEnumValue());
System.out.println(MapEnumSample.getEnumKey("One of the most beautiful cars in the world!"));
System.out.println(MapEnumSample.Mercedes.getEnumValue());
// doesnt exist in Enum
System.out.println("Mustang or Mercedes, which one is the best?");
System.out.println(MapEnumSample.getEnumKey("Mustang or Mercedes, which one is the best?") == null ? "I don't know!" : "I believe that "
+ MapEnumSample.getEnumKey("Ferrari or Mustang, which one is the best?") + " is the best!.");
// exists in Enum
System.out.println("Ferrari or Mercedes, wich one is the best?");
System.out.println(MapEnumSample.getEnumKey("Ferrari or Mercedes, which one is the best?") == null ? "I don't know!" : "I believe that "
+ MapEnumSample.getEnumKey("Ferrari or Mercedes, which one is the best?") + " is the best!");
}
}

You can simply use:
""+ Modes.mode1

public enum Environment
{
PROD("https://prod.domain.com:1088/"),
SIT("https://sit.domain.com:2019/"),
CIT("https://cit.domain.com:8080/"),
DEV("https://dev.domain.com:21323/");
private String url;
Environment(String envUrl) {
this.url = envUrl;
}
public String getUrl() {
return url;
}
}
String prodUrl = Environment.PROD.getUrl();
It will print:
https://prod.domain.com:1088/
This design for enum string constants works in most of the cases.

Enum is just a little bit special class. Enums can store additional fields, implement methods etc. For example
public enum Modes {
mode1('a'),
mode2('b'),
mode3('c'),
;
char c;
private Modes(char c) {
this.c = c;
}
public char character() {
return c;
}
}
Now you can say:
System.out.println(Modes.mode1.character())
and see output:
a

package com.common.test;
public enum Days {
monday(1,"Monday"),tuesday(2,"Tuesday"),wednesday(3,"Wednesday"),
thrusday(4,"Thrusday"),friday(5,"Friday"),saturday(6,"Saturday"),sunday(7,"Sunday");
private int id;
private String desc;
Days(int id,String desc){
this.id=id;
this.desc=desc;
}
public static String getDay(int id){
for (Days day : Days.values()) {
if (day.getId() == id) {
return day.getDesc();
}
}
return null;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getDesc() {
return desc;
}
public void setDesc(String desc) {
this.desc = desc;
}
};

This method should work with any enum:
public enum MyEnum {
VALUE1,
VALUE2,
VALUE3;
public int getValue() {
return this.ordinal();
}
public static DataType forValue(int value) {
return values()[value];
}
public String toString() {
return forValue(getValue()).name();
}
}

i found this one is more easy for preventing type error:
public enum Modes {
some-really-long-string,
mode1,
mode2,
mode3;
String str;
Modes(){
this.str = super.name();
}
#Override
#NonNull
public String toString() {
return str;
}
however - this may work when you need to use a String on a log/println or whenever java compiles the toString() method automatically, but on a code line like this ->
// sample method that require (string,value)
intent.putExtra(Modes.mode1 ,shareElement.getMode()); // java error
// first argument enum does not return value
instead as mentioned above you will still have to extend the enum and use .name() in those cases like this:
intent.putExtra(Modes.mode1.name() ,shareElement.getMode());

after many tries I have come with this solution
public static enum Operation {
Addition, Subtraction, Multiplication, Division,;
public String getUserFriendlyString() {
if (this==Addition) {
return " + ";
} else if (this==Subtraction) {
return " - ";
} else if (this==Multiplication) {
return " * ";
} else if (this==Division) {
return " / ";
}
return "undefined";
}
}

You can try this:
public enum Modes {
some-really-long-string,
mode1,
mode2,
mode3;
public String toString(){
switch(this) {
case some-really-long-string:
return "some-really-long-string";
case mode2:
return "mode2";
default: return "undefined";
}
}
}

use mode1.name() or String.valueOf(Modes.mode1)

Efficiently converting java string to its equivalent enum

Given a string i want to get the enum equivalent of it in constant time.
I have a enum defined like the one shown in the question. Best way to create enum of strings?
public enum Strings {
STRING_ONE("ONE"),
STRING_TWO("TWO")
;
private final String text;
/**
* #param text
*/
private Strings(final String text) {
this.text = text;
}
/* (non-Javadoc)
* #see java.lang.Enum#toString()
*/
#Override
public String toString() {
return text;
}
}
If i now get a string (say "TWO"), is there a way to see if it exists and if it exists then is there a way i can define a method that will return the enum value (for example if i pass "TWO", i should be getting back "Strings.STRING_TWO"?

Is Enum.valueOf() not sufficient? How would you imagine being more efficient than that? There's (usually) no need to have an enum STRING_ONE("ONE") - just call enum value ONE and you get .valueOf() lookup for free.
Otherwise, just create a private static Map<String, YourEnum> and provide a similar valueOf() method that looks up against the Map.

Since Enum.valueOf operates on the built-in name of the enum (i.e. "STRING_ONE" and "STRING_TWO") you would need to roll your own "registry" of name-to-enum, like this:
public enum Strings {
STRING_ONE("ONE"),
STRING_TWO("TWO")
;
private static final Map<String,Strings> byName = new HashMap<String,Strings>();
private final String text;
private Strings(final String text) {
this.text = text;
}
static {
for (Strings s : Strings.values()) {
byName.put(s.toString(), s);
}
}
#Override
public String toString() {
return text;
}
public static Strings forName(String name) {
return byName.get(name);
}
}
Demo.
Above, a map from string name to enum Strings is used to do the translation. If the name is not there, null would be returned from the Strings.forName method.

I think you need to change the code to be :
public enum Strings {
STRING_ONE("ONE"), STRING_TWO("TWO");
private String text;
/**
* #param text
*/
private Strings(final String text) {
this.text = text;
}
public String getText() {
return this.text;
}
public static Strings getByTextValue(String text) {
for (Strings str : Strings.values()) {
if (str.getText().equals(text)) {
return str;
}
}
return null;
}
/*
* (non-Javadoc)
*
* #see java.lang.Enum#toString()
*/
#Override
public String toString() {
return text;
}
}
Example :
String test = "ONE";
Strings testEnum = Strings.getByTextValue(test);
now you have testEnum which is enum reference

UML class diagram implementation Address-Addressbook

I have 2 class diagrams, class Address
+forename
+surename
+street
+houseno
+code
+state
+toString
second Addressbook
insert(address: Address)
toString()
searchSurename (surename: string): Address[*]
+searchForename(forename: string): Address[*]
i implemented address:
public class Address {
public static String forename;
public static String surename;
public static String street;
public static int houseno;
public static int code;
public static String state;
public String toString(){
return this.forename + this.surename + this.street + this.houseno + this.code + this.state;
}
How can I implement Addressbook as easy as possible?
EDIT:
public class addressbook{
private static ArrayList<Address> book;
public addressbook(){
book = new ArrayList<Address>();
}
}
EDIT QUESTION:
Am I allowed to add new methods or attributes in a implementation outside the ones that we use in our class diagrams?
EDIT 2:
First try implementing method searchSurename with an ArrayList:
public static String searchSurename(String surename){
boolean exist = false;
if(this.addresses.isEmpty()){
return null;
}
for(int i=0;i<this.addresses.size();i++) {
if(this.addresses.get(i).getSurename() == surename) {
exist=true;
break;
}
if(exist) {
return this.addresses.get(surename);
} else {
return this.addresses.get(surename);
}
}
// return ?!?
}
The Program give me Errors at "this" at any line, maybe a mistake but I cant tell! It Looks a Little bit too difficult, I don't find any implementations where searching through a list is simple.

You could implement it in a way like this. Look at the api for arrayList for using its methods.
public class Adressbook {
List<Adress> adresses = new ArrayList<Adress>();
public Adressbook(){
adresses = new arraylist<Adress>();
}
public insert (Adress adress){
adresses.add(adress)
}
public searchSurename(String Surename){
}
public searchForename(String forename){
}
public String toString(){
}
ArrayList api:
http://docs.oracle.com/javase/7/docs/api/java/util/ArrayList.html

To have unique address use set collection interface
public class Adressbook {
....
private Set<Adress> adresses = null;
public Adressbook(){
adresses = new HashSet<Adress>();
}
public void add(Adress adress){
adresses.add(adress)
}
...
}

We Keep Coding

Java is a programming language and computing platform first released by Sun Microsystems in 1995.

Best way to create enum of strings? - java

What is the best way to have a enum type represent a set of strings? I tried this: enum Strings{ STRING_ONE("ONE"), STRING_TWO("TWO") } How can I then use them as Strings?

Use its name() method: public class Main { public static void main(String[] args) throws Exception { System.out.println(Strings.ONE.name()); } } enum Strings { ONE, TWO, THREE } yields ONE.

Get and set with default values. public enum Status { STATUS_A("Status A"), STATUS_B("Status B"), private String status; Status(String status) { this.status = status; } public String getStatus() { return status; } }

Related

Object to string delimited format

Executing action depending on enum value

Is there any default method for ENUM? [duplicate]

Efficiently converting java string to its equivalent enum

UML class diagram implementation Address-Addressbook

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