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how can replace more then 16 if else-if statement Java

Im trying to make a program that allows the client to input a String. The string length should have 3 characters only and should contain the letters .
My program have to pass through this table and check what this string refers to..
Let's say the client passed this String "AUG", my program should show the name of this String which is "Met".
I made a code, and it worked but it has more then 15 if else-if condition.
My question is : Is there any other way to do it without using if else-if (or switch).
And does polymorphism work in this case ?

Have a look at HashMap
You can build your table with:
Map<String, String> table = new HashMap<>();
table.put("AUG", "Met");
table.put(...);
Then access your table using the user's input:
if(table.containsKey(input)){
return table.get(input);
}

I think I'd go about it with an enum personally (provided performance wasn't a significant concern):
public enum Abbreviations {
Ala("GCU", "GCC", "GCA", "GCG"),
Arg("CGU", "CGC", "CGA", "CGG", "AGA", "AGG")
// ...
;
private final List<String> codons;
private Abbreviations(final String... codons) {
this.codons = Arrays.asList(codons);
}
public boolean contains(final String codon) {
return this.codons.contains(codon);
}
}
And then you can find their matching from the String using something like:
public String find(final String codon) {
for (final Abbreviations abb : Abbreviations.values()) {
if (abb.contains(codon)) {
return abb.name();
}
}
throw new IllegalArgumentException("Unknown codon: '" + codon + "'");
}

You could try an Object Oriented Aproach:
//This is your representation of Codon
//Which has a name e.g. Alanine and an Abreviation object.
public class Codon {
private String name;
private Abreviation abreviation;
public Codon(String name, Abreviation abreviation) {
this.name = name;
this.abreviation = abreviation;
this.abreviation.addCodon(this);
}
#Override
public String toString() {
return "Codon [name=" + name + ", abreviation=" + abreviation + "]";
}
}
import java.util.ArrayList;
import java.util.List;
// This is a representation of an abreviation object
// Which has an abreviation: ALA;
// and the name of the abreviation "Alanine".
public class Abreviation {
private String abreviation;
private String name;
private List<Codon> codons = new ArrayList<>();
public Abreviation(String abreviation, String name) {
super();
this.abreviation = abreviation;
this.name = name;
}
public boolean addCodon(Codon codon) {
return this.codons.add(codon);
}
#Override
public String toString() {
return "Abreviation [abreviation=" + abreviation + ", name=" + name + "]";
}
}
// Here is your program, where it's being build all the Codons structure with your respective Abbreviation.
public class App {
public static void main(String[] args) {
// This is abreviation, it'll will associated with the codon
Abreviation alanine = new Abreviation("Ala", "Alanine");
// Here it's being build the codon CGU, which has abreviation alanine
Codon GCU = new Codon("GCU", alanine);
// Then using toString method it prints what have been done
System.out.println(GCU);
}
}
You can put all of your codons into a List, so you can search and retrieve then.

Having more than one ArrayList

Hello everyone today am trying to do this in my ArrayList and i know it is possible but it is giving me an exception at main. Now am wondering how am i doing it wrong or what is the best way to do it. Am trying to have An ArrayList and inside the ArrayList I have another one and i give it a variable.
import java.util.ArrayList;
import java.util.Collection;
public class Example3 {
public static void main(String[] args) {
ArrayList<ArrayList<Family>> smallFamily = new ArrayList<ArrayList<Family>>();
smallFamily.addAll((Collection<? extends ArrayList<Family>>) (new Family("John",89 )));
smallFamily.addAll((Collection<? extends ArrayList<Family>>) new Family ("Smith", 78)));
for(ArrayList<Family> s: smallFamily){
System.out.println(s);
}
}
Now bellow is my Family Class and in my family this are the values
public class Family {
public String Name;
public int weight;
public Family(String Name, int weight){
this.Name = Name;
this.weight = weight;
}
public String toString(){
return ("The name is " + this.Name + "The weight is: " + this.weight);
}
}}
The exception being thrown when i compile and run my programme is
Exception in thread "main" java.lang.ClassCastException: Examples.Family cannot be cast to java.util.Collection
at Examples.Example3.main(Example3.java:9)
Now am learning Java on my own and don't have anyone i can ask. Any kind of help will be appreciated.

You are trying to convert an object into a collection. This does not work. Rather, you need to do this:
smallFamily.add(new ArrayList<Family>(1) {{add(new Family("", 0));}});
This will create an ArrayList which adds new Family("", 0) when it is created. Then, it will add this arraylist to the smallFamily arraylist.

Now Why you get this line here
smallFamily.addAll((Collection<? extends ArrayList<Family>>) (new Family("John",89 )));
simply it because the computer couldnt understand what you were doing so it casted for you. Or you casted :). Now trying to convert an object into a collection does not work.
Rather you need to try this
public class Example3 {
public static void main(String[] args) {
ArrayList<ArrayList<Family>> smallFamily = new ArrayList<ArrayList<Family>>();
smallFamily.add(new ArrayList<Family>(2222) {{add(new Family("smith ", 0));}});
smallFamily.add(new ArrayList<Family>(333) {{add(new Family("john ", 0));}});
for(ArrayList<Family> s: smallFamily){
System.out.println(s);
}
}
}
when you add your Family Class
public class Family {
public String Name;
public int weight;
public Family(String Name, int weight){
this.Name = Name;
this.weight = weight;
}
public String toString(){
return ("The name is " + this.Name + "The weight is: " + this.weight);
}
}
The output should be
[The name is smith The weight is: 0]
[The name is john The weight is: 0]
Hope thats what you anticipated.

Data Structure of the Periodic Table of Elements

My goal is to use the periodic table of elements (or a list) to get information about a specific element in Java. I want to search it by atomic number and symbol (but that conversion should be simple).
I found that information in this JQuery plugin. But it is stored as a JSON file.
It seems like it would be most efficient to hardcode the information (since it doesn't change too often and due to performance reasons), but how do I convert JSON to a hardcoded enum?

Since:
the information about elements is totally static
each elemental symbol is alphanumeric
the discovery of new elements is both rare and irrelevant (because they are extremely unstable)
An enum seems a good option:
public enum Element {
H(1, "Hydrogen", 1.008, -259.1),
He(2, "Helium", 4.003, -272.2),
Li(3, "Lithium", 6.941, 180.5),
// ... 90+ others
;
private static class Holder {
static Map<Integer, Element> map = new HashMap<Integer, Element>();
}
private final int atomicNumber;
private final String fullName;
private final double atomicMass;
private final double meltingPoint;
private Element(int atomicNumber, String fullName, double atomicMass, double meltingPoint) {
this.atomicNumber = atomicNumber;
this.fullName = fullName;
this.atomicMass = atomicMass;
this.meltingPoint = meltingPoint;
Holder.map.put(atomicNumber, this);
}
public static Element forAtomicNumber(int atomicNumber) {
return Holder.map.get(atomicNumber);
}
public int getAtomicNumber() {
return atomicNumber;
}
public String getFullName() {
return fullName;
}
public double getAtomicMass() {
return atomicMass;
}
public double getMeltingPoint() {
return meltingPoint;
}
}
There's a bit of java kung fu going on here that deserves an explanation. The map is put inside a static inner (holder) class so it gets initialized before the enum instances are initialized, that way they can add themselves to it. If not in the inner static class, it would not be initialize, because the first thing initialized in the enum class must be the instances, but static inner classes are initialized before the class is initialized.
This approach means the the instances don't need to be listed in any particular order (they could be alphabetical listed, or otherwise).

Suppose you have a PeriodicTable.txt file with following format:
ATOMIC_NUMBER SYMBOL OTHER_INFO
Like:
1 H Hydrogen -> Lightest element
2 He Helium -> Second lightest element
3 Li Lithium -> Third lightest element
// and so on...
Then you can have a fairly straightforward implementation of your own PeriodicTable like following:
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;
public class PeriodicTable
{
private List<Element> elements;
public PeriodicTable() throws IOException
{
elements = new ArrayList<>();
List<String> list = Files.readAllLines(Paths.get("PeriodicTable.txt"));
list.forEach(this::process);
}
public static void main(String[] args) throws IOException
{
final PeriodicTable periodicTable = new PeriodicTable();
System.out.println(periodicTable.getElementByNumber(1));
System.out.println(periodicTable.getElementBySymbol("Li"));
}
private void process(String line)
{
try (Scanner scanner = new Scanner(line))
{
int atomicNumber = scanner.nextInt();
String symbol = scanner.next();
String info = scanner.nextLine();
elements.add(new Element(atomicNumber, symbol, info));
}
}
public Element getElementByNumber(int atomicNumber)
{
return elements.stream().
filter(e -> e.atomicNumber == atomicNumber).
findFirst().orElse(null);
}
public Element getElementBySymbol(String symbol)
{
return elements.stream().
filter(e -> e.symbol.equals(symbol)).
findFirst().orElse(null);
}
private class Element
{
private String info;
private int atomicNumber;
private String symbol;
public Element(int atomicNumber, String symbol, String info)
{
this.atomicNumber = atomicNumber;
this.symbol = symbol;
this.info = info;
}
public String toString()
{
return "[ " + atomicNumber + " " + symbol + " " + info + " ]";
}
}
}
If you see, I have created an Element class which holds the atomic number, symbol, and info of the element, and I have a list of elements in PeriodicTable class.
I read the PeriodicTable data from the PeriodicTable.txt file and process each line of the text file by parsing it appropriately and creating element for each line and adding it to the elements.
I also add two methods for filtering the element based on atomic number and symbol properties.
The code works in Java 8, so you should have at least that to run it, or one can easily write a code for this which will run on earlier JVMs, though it won't be as compact as this one.
Since there are just limited number of elements in the PeriodicTable, I don't bother to have elements sorted by their atomic number though they will be if your PeriodicTable.txt file has elements with increasing atomic number.
Since we know the exact number of elements in the PeriodicTable and its something that doesn't change frequently, the filtering methods take constant time.
All you have to do now is create a proper PeriodicTable.txt file which can then be used by the program.
Note: The PeriodicTable class can be written in better ways as well. This is just an example. I can have it as Singleton. I can even have enum of Element with hardcoded values, but I think loading data from file will keep the code cleaner.
One can even augment the PeriodicTable class with additional properties to each Element, by changing the process() method accordingly, and changing the format of the text file based on the assumptions, and augmenting the Element class, so that it can hold even more information.
Just for fun, following is a Singleton based solution:
// PeriodicTable.java
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;
public class PeriodicTable
{
private static PeriodicTable periodicTable = new PeriodicTable();
private List<Element> elements;
private PeriodicTable()
{
try
{
elements = new ArrayList<>();
List<String> list = Files.readAllLines(Paths.get("PeriodicTable.txt"));
list.forEach(this::process);
}
catch (IOException e)
{
e.printStackTrace();
}
}
public static Element getElementByNumber(int atomicNumber)
{
return periodicTable.elements.stream().
filter(e -> e.atomicNumber == atomicNumber).
findFirst().orElse(null);
}
public static Element getElementBySymbol(String symbol)
{
return periodicTable.elements.stream().
filter(e -> e.symbol.equals(symbol)).
findFirst().orElse(null);
}
private void process(String line)
{
try (Scanner scanner = new Scanner(line))
{
int atomicNumber = scanner.nextInt();
String symbol = scanner.next();
String info = scanner.nextLine();
elements.add(new Element(atomicNumber, symbol, info));
}
}
private class Element
{
private String info;
private int atomicNumber;
private String symbol;
public Element(int atomicNumber, String symbol, String info)
{
this.atomicNumber = atomicNumber;
this.symbol = symbol;
this.info = info;
}
public String toString()
{
return "[ " + atomicNumber + " " + symbol + " " + info + " ]";
}
}
}
// Demo.java
public class Demo
{
public static void main(String[] args)
{
System.out.println(PeriodicTable.getElementByNumber(1));
System.out.println(PeriodicTable.getElementBySymbol("Li"));
}
}
Now you can use your PeriodicTable safely and directly as shown in the Demo method.

Instantiating and Updating Several Objects

Currently I am teaching myself Java but I came across a simple problem but have no one to ask from. From one of the exercises, I wrote a class and write a driver class that instantiates and updates several objects. I am confused by "instantiates and updates several objects." Here is what I mean: So here is my class:
public class PP43Car {
private String make = "";
private String model = "";
private int year;
public PP43Car(String ma, String m, int y)
{
make = ma;
model = m;
year = y;
}
public void setMake(String ma)
{
make = ma;
}
public String getMake()
{
return make;
}
public void setModel(String m)
{
model = m;
}
public String getModel()
{
return model;
}
public void setYear(int y)
{
year = y;
}
public int getYear()
{
return year;
}
public String toString()
{
String result = "Make of the vehicle: " + make +
" Model of the vehicle " + model +
" Year of the vehicle: " + year;
return result;
}
}
Which instantiates make, model and year. Then once I was writing the driver class, the way I began was:
import java.util.Scanner;
public class PP43CarTest {
public static void main(String[] args) {
PP43Car car1;
Scanner scan = new Scanner(System.in);
System.out.println("Enter the model of the vehicle:");
car1.getModel();
}
}
But this class produces error and here is where I am stuck. Do I keep on going with this or is this what is meant by "instantiating and updating several objects?"
import java.util.Scanner;
public class PP43CarTest {
static PP43Car car1;
public static void main(String[] args) {
//Scanner scan = new Scanner(System.in);
car1 = new PP43Car("Millenia", "Mazda", 2011);
}
}
If the above code is correct, then can anyone show me how I can use the Scanner class to actually get the user input and update it that way because I would like to learn that as well?

Well, in your last fragment of code you are indeed instantiating an object, since you are doing:
car1 = new PP43Car("Millenia", "Mazda", 2011);
When you create a new object, you are creating a new instance of the class, so yes, you are instantiaing an object.
But you aren't updating it anywhere, because I think here updating means modifying the object, but you only create the object, not modify it...
Something like this would be an update:
car1.setYear(2013);
Since you are setting a different value for an attribute of the object, you are updating it...
EDIT: Try this code, it can't throw any exception, it's Java basics! I hope it clarifies your doubts...
public class PP43CarTest {
public static void main(String[] args) {
//Declaring objects
PP43Car car1;
PP43Car car2;
PP43Car car3;
//Instantiating objects
car1 = new PP43Car("Millenia", "Mazda", 2011);
car2 = new PP43Car("Aaaa", "Bbb", 2012);
car3 = new PP43Car("Ccc", "Ddd", 2012);
//Updating objects
car1.setMake("Xxx");
car1.setMake("Yyy");
car1.setYear(2013);
//Printing objects
System.out.println("CAR 1: " + car1.toString());
System.out.println("CAR 2: " + car2.toString());
System.out.println("CAR 3: " + car3.toString());
}
}

Instanceof and Casting, Polymorphism

Based on a older question of mine Link I'm working on learning more about Casting and Instanceof. That is based upon a scenario described in a HeadFirst book
So basically I've now got a new class(Hybrid) that inherits from my Vehicle class what i'm trying to do is cast a Hybrid Object to display the extra information that comes with being a hybrid. It complies but doesn't really give me any idea what is causing the error except it just ends on the line i've marked.
public class ShowroomDriver {
public static void main(String[] args) {
Showroom cars = new Showroom("Cars");
Hybrid hybrid1 = new Hybrid("Toyota Prius", "Focus", "John Smith", "TOTAP453453987346283",
getCalendar(2,3,1998), getCalendar(24,2,2012),
"Right Hand",//Hybrid Only Info Edit: Forgot to commentout
true,
'C',
650, 82.0); //Cost & (Hybrid MPG)
cars.addVechicle(hybrid1);
cars.getVechicles();
Hybrid Class
import java.util.Calendar;
public class Hybrid extends Vehicle{
private double consumption;
private String drive;
public Hybrid(String Manufacture, String Model, String CustomerName, String Vin,
Calendar DateManufactured, Calendar Datesold, String Drive,
boolean HasbeenSold,
char TaxBand,
double Cost, double Consumption){
super(Manufacture, Model, CustomerName, Vin, DateManufactured, Datesold,
HasbeenSold,
TaxBand,
Cost);
this.consumption = Consumption;
this.drive = Drive;
}
public Double getConsumption() { return this.consumption; }
public String getDrive() { return this.drive; }
}
New Vehicle Method
public void displayDetails(){
for(int i = 0; i <cars.theVehicles.size(); i++){
if(this.cars.theVehicles.get(i) instanceof Hybrid){//Error here
Hybrid thehybrids = (Hybrid)this.cars.theVehicles.get(i);
System.out.println("Consumption: " + thehybrids.getConsumption()+ "\n" +
"Drive: " + thehybrids.getDrive());
}
}
}

Do you need to cast ? You've already overridden the displayDetails() method to display hybrid-specific info. So you should just be able to call this and the runtime will determine the correct method to call.