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How do I convert java.sql.Array to List<MyCustomEnum>?

I have rs.getArray("lang"); which is java.sql.Array and the lang field is character varying[]. I want to convert it to List<MyEnumLanguage>. As an example I have {fr_FR,en_US} and I have used the following code to convert that my IDE didn't show any errors
List<MyEnumLanguage> myEnumLanguageList = (List<MyEnumLanguage>) rs.getArray("lang");
but it throws an exception org.postgresql.jdbc.PgArray cannot be cast to java.util.List.
My MyEnumLanguage is like:
public enum MyEnumLanguage {
en_US {
public String getCode() { return "en_US" }
},
de_DE {
public String getCode() { return "de_DE" }
};
private MyEnumLanguage() {
}
}

You cannot cast an array to List. Your IDE does not show any arror because casting happens on runtime.
Instead, you should use Arrays.asList(array) method, which returns a list containing all the elements of the array.
Note that if you want to map the elements of the array to another type, you could easily do that with streams. Example:
List<MyEnumLanguage> myEnumLanguageList = Arrays.asList(rs.getArray("lang"))
.stream()
.map(arrayElement -> convertToMyEnumLanguage(arrayElement))
.collect(Collectors.toList());
where convertToMyEnumLanguage() takes an element of your array and returns the corresponding MyEnumLanguage.
Take a look at this post: https://stackify.com/streams-guide-java-8/
UPDATE
Initially I missread the question. You have to first convert your PgArray to a normal java array, before you can use it in Arrays.asList().
This can be done using PgArray.getArray() method, and then cast the returned object to an array of the pgArray's containing type.
UPDATE 2
Improved example:
First of all you should define your enum like this:
public enum MyEnumLanguage {
en_US("en_US"),
de_DE("de_DE");
private final String code;
private MyEnumLanguage(String code) {
this.code = code;
}
public String getCode() {
return code;
}
public static MyEnumLanguage getEnumByCode(String code) {
if(code == null || code.isEmpty()) {
return null;
}
for(MyEnumLanguage e : values()) {
if(e.getCode().equals(code)) {
return e;
}
}
return null;
}
}
Then to map your pgArray to a List:
Array pgArray = rs.getArray("lang");
String[] langJavaArray = (String[]) pgArray.getArray(); //this returns an Object, so we cast it to a String array
List<MyEnumLanguage> myEnumLanguageList =
Arrays.stream(langJavaArray)
.map(MyEnumLanguage::getEnumByCode)
.collect(Collectors.toList())
;
Please note that the mapping function does not check for nulls. So if a wrong codes are passed, your list will contain nulls. If this is not the desired result, you have to perform the appropriate checks and handle null cases in your map function.

Sort Array list of objects based on object attributes

I have list which contains a property class object, In the list i have 3 status
not_paid
paid
part_paid
I want to sort my list below mentioned order.
First - not_paid
second- part_paid
third -paid
How can I sort my list using Comparator class.?
public static Comparator<OrderHistoryItemData> COMPARE_BY_PAYMENT = new Comparator<OrderHistoryItemData>() {
public int compare(OrderHistoryItemData one, OrderHistoryItemData other) {
String p1 = one.getAttributes().getFieldPaymentStatus();
String p2 = other.getAttributes().getFieldPaymentStatus();
if (p1.equals(p2)) {
return 0;
}
if (p1.equals("not_paid") && (p2.equals("part_paid") || p2.equals("not_paid"))) {
return -1;
}
if (p1.equals("not_paid") && p2.equals("not_paid")) {
return -1;
}
return 1;
}
};
This is my Code. i am getting below order using this code.
paid-->not_paid-->part_paid
This is my Update Code. I got my result.
public static Comparator<OrderHistoryItemData> COMPARE_BY_PAYMENT = new Comparator<OrderHistoryItemData>() {
public int compare(OrderHistoryItemData one, OrderHistoryItemData other) {
String p1 = one.getAttributes().getFieldPaymentStatus();
String p2 = other.getAttributes().getFieldPaymentStatus();
if (p1.equals(p2)) {
return 0;
}
if (p1.equals("not_paid") && (p2.equals("part_paid") || p2.equals("paid"))) {
return -1;
}
if (p1.equals("part_paid") && p2.equals("paid")) {
return -1;
}
return 1;
}
};

To avoid complex comparator, I encourage you to export your statuses to an enum. (Plus this will work if you will add more statuses in the future, without the need to change logic in your comparator):
enum PaymentStatus { // Write them in order you want to be sorted
NOT_PAID,
PART_PAID,
PAID
}
Then sorting will be as simple as :
list.sort(Comparator.comparing(item ->item.getAttributes().getFieldPaymentStatus()));

What you can do is first mapping the strings to integers in the desired order, and then simply subtracting them from eachother.
private static Comparator<Payments> comparator = new Comparator<Payments>() {
// Use this mapping function to map the statuses to ints.
// The lowest number comes first
private int map(String str) {
switch (str) {
case "not_paid":
return 0;
case "part_paid":
return 1;
case "paid":
return 2;
default:
return 3;
}
}
// Alternatively, you can use the Map interface to define the sorting
// order.
#Override
public int compare(Payments o1, Payments o2) {
return map(o1.status) - map(o2.status);
}
};
I suggest – Schidu Luca already mentioned it in his answer – that you use enums to define a fixed set of known values, like payment statuses. This provides compile-time safety.
Note: I wouldn't, however, suggest to bind the enum declaration order to the sorting order.

Search for an object in arrayList Java

package generics;
import java.util.ArrayList;
import java.util.List;
public class Generics {
private static List <Box> newlist = new ArrayList<>();
public static void main(String[] args) {
newlist.add(new Box("charlie",30));
newlist.add(new Box("max",29));
newlist.add(new Box("john",22));
// Testing method find -- Start
find ("max",29);
//Testing method find2 -- Start
Box <String,Integer> search = new Box("max",29);
find2(search);
}
public static void find (String parameter, Integer parameter1){
for (Box e : newlist){
if(e.getName() != null && e.getMoney() !=null
&& e.getName().equals(parameter)
&& e.getMoney().equals(parameter1)){
System.out.println("found on position " + newlist.indexOf(e));
break;
}
}
}
public static void find2 (Box e){
for (Box a : newlist){
if (a.equals(e)){
System.out.println("Found");
}else {
System.out.println("Not found");
}
}
}
}
public class Box<T , D>{
private T name;
private D money;
public Box(T name, D money) {
this.name = name;
this.money = money;
}
public T getName() {
return name;
}
public D getMoney() {
return money;
}
#Override
public String toString() {
return name + " " + money;
}
}
Can someone show me how to search for an object in ArrayList.
Method find() it works perfect but in my opinion is wrong and
the reason why I am thinking like that, because I am passing as parameter a string and an integer but should be an box object or maybe I wrong?
In my second method find2() I am trying to pass as parameter an object of Box and when I am trying to search for it I got a false result =(
I am noobie I am trying to understand and to learn.

Stop using raw types!
Box is generic, so if you are not targeting older Java versions, always add generic parameters!.
The declaration of find2 should be like this:
public static void find2 (Box<String, Integer> e)
And you should check whether two boxes are equal in exactly the way you did in find. equals will not work because you did not define an equals method in Box. So:
for (Box<String, Integer> a : newlist){
if (a.getName().equals(e.getName()) &&
a.getMoney().equals(e.getMoney())){
System.out.println("Found");
}else {
System.out.println("Not found");
}
}

You should override Object.equals() on the Box class.
Try to handle null correctly too. Because 2 Box with null names and/or null money are in fact equal.
(you DON'T need to override Object.hashCode() for this, but it's a good practice to do so, just in case it is used in a hashmap or hashset or such).

The easiest way to search and find something in an arraylist is to use the .equals method combined with a for loop to iterate through your lists.
for(int i = 0; i < newList; ++i)
{
if(newlist.equals(Stringname))
{
//it matches so do something in here
}
}
what it is doing here is moving through the list 1 by 1 until it finds something that matches what you entered -> stringName

How to remove if else condition from loop?

I have a code snippet similar to the one below,
public ArrayList getReport(reportJDOList,accountType)
{
String abc = "";
for(ReportJDO reportJDO : reportJDOList)
{
if(accountType.equals("something")
abc = reportJDO.getThis();
else
abc = reportJDO.getThat();
//somecode goes here
}
returning List;
}
As I know the value of accountType before the iteration, I dont want this check to happen, for every entry in a list as it would cause numerous number of checks if the size of reportJDOList is 10000 for an instance. How we remove this thing from happening? Thanks in Advance :)

You can indeed peform check once and implement 2 loops:
if(accountType.equals("something") {
for(ReportJDO reportJDO : reportJDOList) {
abc = reportJDO.getThis();
}
} else {
for(ReportJDO reportJDO : reportJDOList) {
abc = reportJDO.getThat();
}
}
Obviously you can improve your design by either
separating you loops into 2 different methods
Using command pattern, i.e. implementing loop body in different command and executing it to loop.
Using Guava's Function (it is just improvement of #2)
Using java 8 streams.

IF you want to save the String comparison, make it once before the loop and store the result in a boolean variable :
String abc = "";
boolean isThis = accountType.equals("something");
for(ReportJDO reportJDO : reportJDOList) {
abc = isThis ? reportJDO.getThis() : reportJDO.getThat();
//somecode goes here
}

I'd vote for clean coding this - perform the check once and delegate the logic into private methods, each performing the loop individually. This duplicates code for the loop but gives greatest flexibility if at some point you need to do something more in SomethingReport that's not duplicated in OtherReport.
public ArrayList getReport(reportJDOList,accountType) {
if("soemthing".equals(accountType)) {
return getSomethingReport(reportJDOList);
} else {
return getOtherReport(reportJDOList);
}
}
private ArrayList getSomethingReport(reportJDOList) {
[...]
}

interface AccountHandler {
String get(Report r);
}
AccountHandler thisHandler= new AccountHandler() {
#Override
public String get(Report r) {
return r.getThis();
}
};
AccountHandler thatHandler= new AccountHandler() {
#Override
public String get(Report r) {
return r.getThat();
}
};
//...............
AccountHandler ah;
ah = (what.equalsIgnoreCase("this")) ? thisHandler : thatHandler;
Report r=new Report();
// loop
ah.get(r);

//Using reflection:
Report r = new Report();
Method thisMethod = r.getClass().getDeclaredMethod("getThis");
Method thatMethod = r.getClass().getDeclaredMethod("getThat");
Method m = (what.equalsIgnoreCase("this")) ? thisMethod : thatMethod;
m.invoke(r);

Java String contain method and enum

I have enum defined in class as
public enum EnumSample {
SPACE,
NASA,
SPUTNIK;
}
In class Test, I have a method with following code snippet
if (str.contains(<>)) {
Is it possible to search all enum values in contain method of String?

You can iterate over the .values() of the enum and apply .contains() for each of them.
For example:
for (EnumSample value : EnumSample.values()) {
if (str.contains(value.name()) {
//do your thing
}
}

One problem with contains is that it finds parts of words - for example, it would find "NASA" in "NASAL DECONGESTANTS". If you would like your comparison to be fast, and look for specific words, not parts of words, use regex search instead.
The regex for your example would look like this:
\b(SPACE|NASA|SPUTNIK)\b
You can construct and use it like this:
static Pattern allEnumVals;
static {
StringBuilder b = new StringBuilder("\\b(");
boolean first = true;
for (EnumSample e : EnumSample.values()) {
if (!first) {
b.append("|");
} else {
first = false;
}
b.append(e.name());
}
b.append(")\\b");
allEnumVals = Pattern.compile(b.toString());
}
static boolean check(String str) {
return allEnumVals.matcher(str).find();
}