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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.

contains method with list of objects in Java

I have a list of objects "SaleItem". they are all objects of the same class. each object has a String field "name" and an int field "value". I want to see if one of the objects contains a name. It seems that I can't use the "contains" method to do this. I see two solutions. one is to iterate through all the objects to check if one has said name:
for (SaleItem item: myList) {
if (item.getName() == "banana") {
// do stuff
}
}
The other solution would be to create a new list of Strings from "myList" and use the contains method on that:
ArrayList<String> nameList = new ArrayList<>();
for (SaleItem item: myList) {
nameList.add(item.getName());
}
if (nameList.contains("banana")) {
// do stuff
}
I imagine the first method would be most efficient if I'm only doing it once, and the second would be more efficient if I'm doing it many times. Being a bit of a newbie without a formal education, I don't know what's proper in this situation.

Since SaleItem.getName() returns a string, you should be able to use "contains" method.
It seems like you have initialized the ArrayList or the SaleItem object incorrectly.
public class TestApp {
public static void main(String[] args) {
List<SaleItem> list = new ArrayList<SaleItem>();
SaleItem s1 = new SaleItem();
s1.setName("banana");
s1.setValue(1);
SaleItem s2 = new SaleItem();
s2.setName("apple");
s2.setValue(2);
list.add(s1);
list.add(s2);
for (SaleItem item: list) {
if (item.getName().contains("banana")) {
System.out.println("Pass");
}
}
}
}
class SaleItem {
private String name;
private int value;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getValue() {
return value;
}
public void setValue(int value) {
this.value = value;
}
}

Try with this code
public class SaleItem {
private String itemName;
public String getItemName() {
return itemName;
}
public SaleItem setItemName(String itemName) {
this.itemName = itemName;
return this;
}
#Override
public String toString() {
return "[SaleItem : { itemName = " + this.getItemName() + " }]";
}
public static void main(String[] args) {
ArrayList<SaleItem> nameList = new ArrayList<>();
nameList.add(new SaleItem().setItemName("banana"));
nameList.add(new SaleItem().setItemName("grape"));
nameList.add(new SaleItem().setItemName("watermelon"));
nameList.add(new SaleItem().setItemName("orange"));
nameList.add(new SaleItem().setItemName("guava"));
for (SaleItem item : nameList) {
if (item.toString().contains("banana")) {
// Do this
}
}
}
}

A List's .contains method isn't magical, it will generally just loop through the elements checking for equality, O(n) linear performance.
Your first solution is probably fine.
If you really did expect repeated access and wanted better than linear performance on subsequent lookups, you'd probably want to construct a Map<String,SaleItem>, or a Set<String> depending on what you wanted to do with it. But those solutions would normally only work on exact matches. Once you need case-insensitive matches, they have to be TreeMap or TreeSet with a case-insensitive comparator. And if you want partial matching (like using String.contains() or a regular expression), you'd want to go back to a linear search.
But don't do any of that unless you have to. Keep it simple.

Multiple values for a single parameter

How to pass multiple values to a single parameter for a particular method in java.
e.g. suppose i have a method with single parameter 'childname', that gets names of all the children in a family.
Now how can i pass multiple values to this parameter to get all different names.
public String getChildrenNames(String childname)
{
children= childname+ familyName;
return children;
}

You would typically implement this using either an Array, or a Collection.
eg:
public String[] getNamesOfChildren()
or
public Collection<String> getNamesOfChildren()

As people say you need to pass them as an Array, so your code should be like this:
String familyName = "Family";
public String[] getChildrenNames(String[] childnames)
{
String[] result = new String[childnames.length];
for(int i=0; i<childnames.length; i++)
{
result[i] = childnames[i] + " " +familyName;
}
return result;
}
public void main()
{
String[] childnames = {"Name1", "Name2", "Name3"};
String[] childnamesAux = getChildrenNames(childnames);
}
With this your childnamesAux variable should have: {"Name1 Family", "Name2 Family", "Name3 Family"}

If you can't change the signature of your method, then you can use concatenation, then in your method you can split this parameter for example :
String childname = firstname + "," + lastname;
getChildrenNames(childname);
so you can split this parametter to get multiple names,
String[] spl = childname.split(",");
But there are better ways then this, if you can change the signature of your method, so you can create a method which can take an array or list of names instead :
public String getChildrenNames(String...childnames) {
or
public String getChildrenNames(Lis<String> childnames) {
You can even create an Object for example :
class Person{
private String firstname;
private String lastname;
//getters and setters
}
Then your method should take an array or a list of Person Object :
public String getChildrenNames(List<Person> childname) {

You can try this
public static String child(String... name){
String[] array=name;
String tem;
if(name.length==1)
return name[0];
for(int counter=0; counter<array.length;counter+=2){
array[0]=name[counter]+name[counter+1];
}
tem=array[0];
return tem;
}
now if you call it
child("Paul","walker");
the output will be
Paul Walker
hope this helped

you can use var args like below
public String getChildrenNames(String... childname)
{
for(String s:childname)
{
children= childname+ s;
}
return children;
}
example
public class Test {
public static void main(String[] args) {
System.out.println(tes("s","d","s"));
}
static String tes(String... x)
{
String y="";
for(String s:x)
{
y=y+s;
}
return y;
}
}
output: sds

If JComboBox is editable, how to cast the entered string to object?

So I have this class "Member" :
package pkgData;
import java.io.Serializable;
public class Member implements Comparable<Member>, Serializable{
/**
*
*/
private static final long serialVersionUID = 1L;
private String name;
private String city;
public Member(String nameOfMember,String location) {
super();
this.name = nameOfMember;
this.city=location;
}
public String getNameOfMember() {
return name;
}
public String getLocationOfMember() {
return city;
}
public void setNameOfMember(String nameOfMember) {
this.name = nameOfMember;
}
#Override
public String toString() {
return name +", " + city;
}
#Override
public int compareTo(Member o) {
int result =this.getNameOfMember().compareTo(o.getNameOfMember());
if(result==0){
result = this.getLocationOfMember().compareTo(o.getLocationOfMember());
}
return result;
}
}
And I have a JComboBox which is EDITABLE and the model of the ComboBox is DefaultComboBoxModel.
So the problem is that if I cast the selectedItem:
Member nameOfMember = (Member)memberModel.getSelectedItem();
if(nameOfMember== null)
throw new Exception("please select a name and a location");
It only checks if the entered string is empty. If I enter a string like "Name, Location" I always get the exception that String cannot be cast to Member. Which String to I have to enter that the String can be cast to Member?
Here is my JComboBox:
private JComboBox<Member> getComboBoxMember() {
if (comboBoxMember == null) {
comboBoxMember = new JComboBox<Member>();
comboBoxMember.setEditable(true);
comboBoxMember.setModel(memberModel);
}
return comboBoxMember;
}
and here the global variables:
private DefaultComboBoxModel<Member> memberModel;
private JComboBox<Member> comboBoxMember;

String nameOfMember = (String) memberModel
.getSelectedItem();if(nameOfMember==null)throw new Exception("please select a name and a location");else
{
String[] parts = nameOfMember.split(",");
String part1 = parts[0]; // name
String part2 = parts[1]; // location
Member member=new Member(part1, part2);
}

String split & cast method
What you can do is first of all test if the string you get is null, or if it matches well you format. Then, you can create a new object with these elements.
Here's a small example code :
String memberData = (String)memberModel.getSelectedItem();
if(memberData == null || memberData.split(", ")[0].isEmpty() || memberData.split(", ")[1].isEmpty()) {
throw new Exception("Data is incorrect, please provide name and location separated with ", ");
}
Member member = new Member(memberData.split(", ")[0], memberData.split(", ")[1]);
JComboBox method
With Java 7 happened a new possibility of extension to JComboBox, which can now be generically parameterized (as for ArrayLists) in the form JComboBox<Type>. Thus, the objects you can get with getSelectedItem() can now be casted to the generic type you gave in parameter to JComboBox. The only problem is that, when a JComboBox is edited, as in your case, the data is casted to a simple String.
What you can do in your listener method (I will use ActionListener) is the following :
class ItemAction implements ActionListener {
#Override
public void actionPerformed(ActionEvent e) {
try {
//In case the user has not modified the object
Member member = (Member)box.getSelectedItem();
//Just an example here
if(member != null) {
System.out.println(member.toString());
}
} catch(ClassCastException ex) {
//In case the object has been modified
String data = (String)box.getSelectedItem();
//Apply first method here
}
}
}
But the problem with this method is that you end up using the first method still.

Arraylist add object by setter

I have created ArrayList and make setter and getter for it.
In the other class i want to add objects in this array. But my code doesn't works. i think i need to add in method setter for array some other code..
public class DataVar {
private ArrayList<String> arrayLinks = new ArrayList<>();
public ArrayList<String> getArrayLinks() {
return arrayLinks;
}
public void setArrayLinks(ArrayList<String> arrayLinks) {
this.arrayLinks = arrayLinks;
}
}
//Here is another class
public class LinksAd {
public void getAllLinksAd() {
DataVar dataVar = new DataVar();
String link = "href";
dataVar.setArrayLinks(link) }}

Looking at your code you are trying to add a String type, where your code specifies that you are expecting an ArrayList. Assuming you just want to add a string to your arraylist the following will work:
public void setArrayLinks(String arrayLinks) {
this.arrayLinks.add(arrayLinks);
}

You can implement generic setter method.
This is DataVar class:
public class DataVar {
private List<String> itemList=new ArrayList<String>();
public List<String> getItemlist() {
return itemList;
}
public void setItemList(Object list) {
if (list.getClass().equals(String.class)) {
itemList.add((String)list);
}
else if (list.getClass().equals(ArrayList.class)) {
itemList = (ArrayList<String>)list;
}
else {
throw new Exception("Rejected type- You can set String or ArrayList");
}
}
}
And this is calling setter method example:
Main class:
public static void main(String[] args) {
List<String> exampleList = new ArrayList<String>();
exampleList.add("This example");
exampleList.add("belongs to");
String owner = "http://www.javawebservice.com";
DataVar dataVar = new DataVar();
dataVar.setItemList(exampleList);
dataVar.setItemList(owner);
for(String str:dataVar.getItemlist()){
System.out.println(str);
}
}
Output:
This example
belongs to
http://www.javawebservice.com
So, you can set ArrayList, also you can set String.

You could do a mehtod to add an Item like this:
public void addStringToList(String s)
{
arrayLinks.add(s);
}
In LinksAd you have to wirte:
dataVar.addStringToList(link);