Develop Reference

How to get Path variable in spring filter or java

I want to get {testId : 111} from /v1/testId/111 example URL.
I know that it is very simple to get path variable if using the request.getAttribute(HandlerMapping.URI_TEMPLATE_VARIABLES_ATTRIBUTE) method.
But, filters are executed before Servlets.
Therefore, request.getAttribute(HandlerMapping.URI_TEMPLATE_VARIABLES_ATTRIBUTE) method is not available.
(ref. How to get Path Variables in Spring Filter?)
Is there any way to retrieve Path Variable within the filter?
Or, Is there any way to retrieve Path Variable without request.getAttribute(HandlerMapping.URI_TEMPLATE_VARIABLES_ATTRIBUTE) method?
The String of /v1/testId/111 is actually available and I intend to extract 111 from it.

You are looking for lastIndexOf, a method of String.
String foo = "/v1/testId/111";
String theValue = foo.substring(foo.lastIndexOf("/") + 1);
lastIndexOf returns the numerical position of the last slash in this case and getting the substring from the next numerical position will effectively return everything you have after the last slash.
EDIT
If you have more instances, like /v1/testId/111/userId/222, then you could split your String, like
String string = "/v1/testId/111/userId/222";
String[] parts = string.split("/");
for (int index = 0; index < parts.length; index++) {
if (isNumeric(parts(index))) {
//Do something with these values as you please
String entityName = parts[index - 1];
String entityValue = parts[index];
}
}
isNumeric is implemented as such:
public static boolean isNumeric(String strNum) {
if ((strNum == null) || (strNum.equals(""))) {
return false;
}
try {
double d = Double.parseDouble(strNum);
} catch (NumberFormatException nfe) {
return false;
}
return true;
}
Courtesy to https://www.baeldung.com/java-check-string-number

Won't return object

private ArrayList players = new ArrayList<Player>();
public Player getPlayerByName(String theName){
for(int i = 0; i < players.size(); i++){
String pName = (String) players.get(i);
if(pName.equals(theName)){
return (Player) players.get(i);
} else{
return null;
}
}
Above is my code. So, the error comes from this method saying that it must return a Player type yet I am doing so after searching for the matching strings. What do you do for this to work? My apologies if this has been answered already.

There are several issues in the presemted code:
List players should contain Player objects, but in the loop the element of the list is cast to String before comparison, and then the same element is cast to Player.
Only the first element in the list is checked, if it's not matched, a null returned
The code should be fixed like this:
private List<Player> players = new ArrayList<>();
public Player getPlayerByName(String theName) {
for (Player player : players) {
String pName = player.getName();
if (pName.equals(theName)) {
return player;
}
}
return null;
}
It may be worth to use Java Stream for this task:
public Player getPlayerByName(String theName) {
return players.stream() // Stream<Player>
.filter(p -> p.getName().equals(theName)) // keep matched by name
.findFirst() // pick the first match
.orElse(null); // provide null if no match is found
}

As your return statement is inside the for loop, you must have a return statement at the end of the function.
Because when the return statement is inside a conditional statement(or a loop), there is a possibility that the condition is false and the program may never reach the return statement.

Duplicate Objects being stored in ArrayList with add method

I have two classes, one named Bird the other Runtime. The bird class creates birds - name, latin name. The Runtime class has 4 methods, only one is important for this question, that is the 'add' method. The add method when called upon needs to take input from the user that is name and latin name, these are saved into a string variable 'name' and 'latin name' and I call the Bird class constructor and pass in these string variables into its parameter and finally it is added to an ArrayList. However I get duplicate values, if I were to write the same bird twice.
I have tried to convert the ArrayList into a set and convert it back again into an ArrayList, i did this within the add method, this did not work. I suspect it is down to my poor understanding of how objects are stored in an ArrayList. I also created a getName method within the Bird class, so I can use list.get(i).getName, and if the name is equal to the one typed by the user, it prompts the user accordingly, if not it is added to my ArrayList. This also did not work. I also tried a for loop that would go through the ArrayList and an if statement would determine if the name typed by the user exists within the ArrayList, this also did not work, the attempt was early on so I can't remember exactly the error message, but the add method is called from within a while loop, and I think the error message was concurrent modification, I'm not entirely sure so please ignore that, my point is showing the various solutions I tried.
Below is The Bird class
public class Bird{
int obeservation = 0;
String name;
String latinName;
public Bird(String name, String latinName){
this.name = name;
this.latinName = latinName;
}
public void addBird(String name, String latinName){
this.name = name;
this.latinName = latinName;
}
public String getName(){
return this.name;
}
public String statistics(){
return this.name + " (" + this.latinName + ") : " +
this.obeservation + " observation";
}
}
Below is the Runtime class
public class Runtime {
ArrayList<Bird> birds = new ArrayList<Bird>();
Scanner scan = new Scanner(System.in);
public void scan() {
System.out.println("?");
String answer = scan.nextLine().trim();
while (!answer.equalsIgnoreCase("EXIT")) {
System.out.println("?");
answer = scan.nextLine().trim().toUpperCase();
if (answer.equalsIgnoreCase("ADD")) {
add();
} else if (answer.equalsIgnoreCase("OBSERVATION")) {
observation();
} else if (answer.equalsIgnoreCase("STATISTICS")) {
System.out.println("jhjh");//just to see if this is
working
statistics();
}
}
}
below is the add method, also what I've commented is the attempts,
currently the add method does not have an if statements to decide duplicates.
public void add() {
System.out.print("Name: ");
String name1 = scan.nextLine().trim().toUpperCase();
System.out.print("Latin Name: ");
String latinName1 = scan.nextLine().trim().toUpperCase();
birds.add(new Bird(name1, latinName1));
/*
Bird newBird = new Bird(name1, latinName1);
for (int i = 0; i < birds.size(); i++) {
if (birds.get(i).getName().equals(name)) {
System.out.println("Bird already exist");
return;
} else {
birds.add(newBird);
}
}
/*
* hBirds.addAll(birds); birds = new ArrayList<Bird>();
birds.addAll(hBirds);
*
* // Bird newBird = new Bird(name, latinName);
* /* if(birds.contains(name)){
* System.out.println("That name already exist");
* return;
* }else{
* birds.add(newBird(name, latinName));
*
* }
*/
}
The statistics method prints out the ArrayList, a foreach loop that goes through the ArrayList prints it out. The expected result if I input seagull twice should be one seagull value not two. How do i reject the duplicate?

You can have two approaches here:
First: Traverse through ArrayList, if you can't find the same bird, add it to ArrayList. It is a worse approach.
Second: Store birds inside HashSet. In this case, you need to override .hashCode() and .equals(Object obj) methods. It is a better approach.
Before talking about how to generate .hashCode() and .equals(Object obj) methods, I want to mention about .hashCode() method and HashSet<T>.
HashSet<T>s provide a unique set of the elements inside. To achieve this, .hashCode() method of a class is used. If you override .hashCode() method in any class, you can get the benefit of using HashSet<T>s. If you don't override this method, Java automatically returns the memory address of the object. That's why your HashSet<Bird> was including duplicate elements.
.hashCode() and .equals() methods can be generated by lots of IDEs. I copied and pasted your Bird class to Eclipse. By using Alt+Shift+S -> h for Eclipse or Alt+Insert -> equals() and hashCode() for IntelliJ, automatically generated the methods below:
#Override
public int hashCode() {
final int prime = 31;
int result = 1;
result = prime * result + ((latinName == null) ? 0 : latinName.hashCode());
result = prime * result + ((name == null) ? 0 : name.hashCode());
result = prime * result + obeservation;
return result;
}
#Override
public boolean equals(Object obj) {
if (this == obj)
return true;
if (obj == null)
return false;
if (getClass() != obj.getClass())
return false;
Bird other = (Bird) obj;
if (latinName == null) {
if (other.latinName != null)
return false;
} else if (!latinName.equals(other.latinName))
return false;
if (name == null) {
if (other.name != null)
return false;
} else if (!name.equals(other.name))
return false;
if (obeservation != other.obeservation)
return false;
return true;
}
If you add these methods(I encourage you to generate in your IDE) to Bird class, you can use HashSet<Bird>. To avoid duplicates, simply add all of your Bird objects into defined HashSet<Bird>. You don't need any other data structure or equality check to control if any two Bird type objects are equal.
You will just need to change your object collection from ArrayList<Bird> birds = new ArrayList<Bird>(); to Set<Bird> birds = new HashSet<>();.

Move the add out of the loop:
for (int i = 0; i < birds.size(); i++) {
if (birds.get(i).getName().equals(name1)) {
System.out.println("Bird already exist");
return;
}
}
birds.add(new Bird(name1, latinName1));

Java: index in array exists, ArrayIndexOutOfBoundsException: 0

Sorry if this is answered somewhere due to me missing something obvious, but I've been googling this for days now and it just doesn't seem to make any sense. I've got 3 years of experience in Javascript and am getting into Java now, so I'm not behind on the basic concepts of anything and such.
I'm using IntelliJ for this, but it fails to point out the problem. The communication (access rights and instantiations) between my classes is fine, the code syntax and variable types are as well, etc, so I really can't tell what it is.
I have a Data class, which just holds "read-only" data for the other classes to use.
public class Data {
// snip
public static int[][] specs = {
{6,1,6,40},
{5,2,5,30},
{5,3,4,40},
{4,4,3,60}
};
}
There's another class that has to read this data when it's initialized.
public class Soldier {
// snip
public int range;
public Soldier() {
int x = ...; // user input
range = Data.specs[x][1];
}
}
The specs array itself contains its data as defined (ie the array is not empty), x is valid as an index of the specs array (ie 0 <= x <= 3), its type is int and Test has read access to the specs array (all confirmed with debug output statements). And yet, when it tries to set the value of range (then and only then, at that exact point), I get the "Index out of bounds" error.
Can someone please tell me what's going wrong when trying to read the array? Or am I right in saying that this is really weird and I need to post the entire code?
Note: a small new test also shows that, if I change the code to first output a manually chosen value from the array and then set the value of range, the console prints the error statement (and exits the program) and follows it up by printing the manually picked value, but assigning the value and then asking to output range only throws the error... That makes absolutely no sense at all!
Edit: I've edited the code above. The class called Test is called Soldier in my code (I'm making a text-based game...). Below's the stack trace, if it's any good without the full code (which is way long). The basic structure of my program is this:
1) Boot contains the main method and instantiates a new Game
2) Game instantiates x Teams
3) each Team instantiates an Army
4) each Army instantiates x Soldiers
Each instance of the classes is set as an attribute of the instantiating class (public Army army; and an Army instantiation in the Team constructor, for example). It's essentially a cascade of constructors instantiating subsequent classes and assigning them as their attributes.
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 0
at Army.<init>(Army.java:13)
at Team.<init>(Team.java:19)
at Game.<init>(Game.java:22)
at Boot.main(Boot.java:15)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:601)
at com.intellij.rt.execution.application.AppMain.main(AppMain.java:120)5
Edit edit: here's the semi-full code (I'm leaving out the stuff that has absolutely nothing to do with it, including the imports). It's in no particular order and the classes are in separate .java files within the IntelliJ project. The game continues up to the point where a new Soldier asks for its type to be designated (the function performing the user input is working fine and validating the input as proven by a technically identical other part of the game).
public class Boot {
public static void main(String[] args) {
Object[] games = new Object[] {};
if (Lib.userConfirmPrompt("Start the game?") == true) {
do {
games[games.length] = new Game();
}
while (Lib.userConfirmPrompt("Do you want to play again?") == true);
}
System.exit(0);
}
}
public class Game {
public Object[] teams = new Object[] {};
public Game() {
for (int i = 0;i < settings.xbots + 1;i++) {
teams[teams.length] = new Team(this);
}
}
}
public class Team {
public Game game;
public Army army;
public Team(Game p) {
game = p;
army = new Army(this);
}
}
public class Army {
public Team team;
public static Object[] soldiers = new Object[] {};
public Army(Team p) {
team = p;
for (int i = 0;i < team.game.settings.xsoldiers;i++) {
soldiers[soldiers.length] = new Soldier(this);
}
}
}
public class Soldier {
private Army army;
public int sight;
public int range;
public int distance;
public int damage;
public Soldier(Army p) {
army = p;
int type = Lib.userTxtIntOptionsPrompt(Data.isoldiertypes);
// HERE is where it crashes, type is assigned and valid but the array access fails
sight = Data.isoldierspecs[type][0];
range = Data.isoldierspecs[type][1];
distance = Data.isoldierspecs[type][2];
damage = Data.isoldierspecs[type][3];
}
}
public class Data {
public static List isoldiertypes = Arrays.asList("Scout","Private","Machinegunner","Grenadier");
public static int[][] isoldierspecs = {
{6,1,6,40},
{5,2,5,30},
{5,3,4,40},
{4,4,3,60}
};
}
public class Lib {
private static Scanner input = new Scanner(System.in);
// output
// default: 1 query string to print
public static void outBase(String query) {
System.out.print(query);
}
public static void outStd(String query) {
outBase(query + "\n");
}
// end of output
// input
// default: 1 query string to print,
// query and input are in-line (exception: userConfirmPrompt prints query block-wise and default instruction in-line before input),
// keeps user hostage until valid input is given (exception: userPrompt returns blindly)
public static String userPrompt(String query) {
outBase(query);
return input.nextLine();
}
public static String userTxtPrompt(String query) {
String menuinput = null;
do {
if (menuinput != null) {
userHostage();
}
menuinput = userPrompt(query);
} while (menuinput.length() == 0);
return menuinput;
}
public static int userIntPrompt(String query) {
String menuinput = null;
do {
if (menuinput != null) {
userHostage();
}
menuinput = userTxtPrompt(query);
} while(menuinput.matches("^-?\\d+$") == false);
return new Integer(menuinput);
}
// end of input
// options input
// default: takes a List of options as argument,
// prints an enumerated list of these options string-wise,
// prompts for a numeral selection of the desired option and returns the number if valid
public static int userTxtIntOptionsPrompt(List options) {
int choice = 0;
Boolean chosen = false;
do {
if (chosen == true) {
userHostage();
} else {
chosen = true;
}
chosen = true;
for (int i = 0;i < options.size() - 2;i++) {
outStd((i + 1) + ") " + options.get(i) + ",");
}
outStd((options.size() - 1) + ") " + options.get(options.size() - 2) + "\nand " + options.size() + ") " + options.get(options.size() - 1) + ".");
choice = userIntPrompt("Enter the number of the option you'd like to select: ") - 1;
} while(choice < 0 || choice >= options.size());
return choice;
}
// end of options input
// miscellaneous
public static void userHostage() {
outStd("Invalid operation. Please try again.");
}
}

The problem is in your Army class:
public static Object[] soldiers = new Object[] {};
You initialize an empty (length == 0) array named soldiers, but later you access:
soldiers[soldiers.length] = new Soldier(this);
This causes the failure.
By definition, soldiers.length is out of the bound of the array (since the bound is from 0 to soldiers.length-1)
To overcome it - make sure you allocate enough space in the array soldiers or use a dynamic array (ArrayList) instead. You can append elements to an ArrayList using ArrayList.add(), and you don't need to know the expected size before filling it up.

The x should be greater than -1 and less than 4.
The stacktrace does not mention the Solder class, its in the conctructor of the Army class.
Any how, only knowing that the index should be within a range is not enough. As a programmer its your duty to validate the index before trying to access an element at that index.
if(index > 0 && index < array.length) {
//then only acess the element at index
Problem is the array soldiers is of size 0.

This line int x = ...; // user input implies that you are taking input in some fashion from the user and accessing the array with it. Are you checking this value to see that is in range (i.e., between 0 and 3)? If not, this may be why your testing works.
Edit: something like this might solve it for you:
public class Army {
public Team team;
public Vector<Soldier> soldiers;
public Army(Team p) {
soldiers = new Vector<Soldier>()
team = p;
for (int i = 0;i < team.game.settings.xsoldiers;i++) {
soldiers.add(new Soldier(this));
}
}
}
Judging by your other code, this sort of pattern will be useful in your Game object as well.

Searching a class array with multiple values per record

I need to search an object array for a Name and then print out all info corresponding to that name.
I have
public class AccessFriendlyFile {
private Friendlies[] fr = new Friendlies[100];
private int size = 0;
public AccessFriendlyFile (){
try {
Scanner scFile = new Scanner(new File("Friends.txt"));
String line, name, surname, cell, mail, landline;
while (scFile.hasNext()){
line = scFile.nextLine();
Scanner sc = new Scanner(line).useDelimiter("#");
name = sc.next();
surname = sc.next();
cell = sc.next();
if (sc.hasNext()){
mail = sc.next();
landline= sc.next();
fr[size] = new ExtendFriendlies(name, surname, cell, mail, landline);
}
else {
fr[size]= new Friendlies(name, surname, cell);
}
size++;
sc.close();
}
}catch (FileNotFoundException ex){
System.out.println("File not found");
}
How do I code a method that will search "fr" for a name and print out all corresponding info?
Many Thanks
Jesse
Edit:
Here is my Search method, that is currently not working.
public int Search(String name) {
int loop = 0;
int pos = -1;
boolean found = false;
while (found == false) {
if (fr[loop] == name) {
found = true;
pos = loop;
} else {
loop++;
}
}
return pos;
}
Incomparable types error on the if statement.

In your Friendlies class, have a method called getName() that will return the name of that Friendly. Iterate through the fr until you find the matching name. Once you've found that name, use similar get methods to print out all the information you want for the matching Friendly you just found.

I would suggest that you rename your variables here. The Friendlies class stores, I think, a single contact, a Friend. The list of Friend objects is an array that you might beter name friendList or even friendlies. I would also encourage you to not use size as a counter variable. Size is how many friends you have, and you can iterate through them using i, or friendCounter, or use a for each loop as I demonstrate below,
public Friendlies find(String name) {
for(Friendlies friend : fr) {
if(friend.getName().equalsIgnoreCase(name))
return fiend;
}
return null;
}
//now to print the info you can do this:
Friendlies findJoe = find("Joe");
if(findJoe==null)
System.out.println("You have no friends namd Joe.");
else
System.out.println(findJoe);
My code assumes that you implement toString() in Friendlies. If you use netbeans, you can auto-generate this code and then tweak it to get the format you want. (Just right-click where you want to write the method and choose insert code)

This should work:
public List<Friendlies> search(String name) {
List<Friendlies> list = new ArrayList<Friendlies>();
for(Friendlies friendlies : fr) {
if(friendlies.getName().equals(name)) {
list.add(friendlies);
}
}
return list;
}
Then, with the returned list, implement a nice display of the data :)

Assuming the AccessFriendlyFile loads the data into your array, you can use a for each loop, if you want to retieve all the matching names :
List<Friendlies> getByName(String searched){
List<Friendlies> result = new Arraylist<Friendlies>();
for (Friendlies currentFriendly : fr){
if (searched.equalsIgnoreCase(currentFriendly.getName()){
result.add(currentFriendly);
}
}
return result;
}
for only the first one :
Friendlies getByName(String searched){
for (Friendlies currentFriendly : fr){
if (searched.equalsIgnoreCase(currentFriendly.getName()){
return currentFriendly;
}
}
return null;
}
You should use lists instead of fixed arrays. If the files contains more than 100 records you'll get an indexoutofbounds exception.