I am writing my first app in Android Studio, I am a self-taught novice. When I write data into the subscript of an array I have created as a user-defined class the value is written into an adjacent subscript as well! Have traced to some code where I move data down one position in the array, thought I could do this in one operation, but it seems this messes something up and I need to copy each member of the class individually.
Here is my class
class LeaderboardClass
{
public String DateTime;
public String UserName;
public long Milliseconds; //0 denotes not in use
}
Here is my array declaration
LeaderboardClass[] LeaderboardData = new LeaderboardClass[LeaderboardEntries];
I want to move some data from subscript j to subscript j+1
I tried
LeaderboardData[j + 1] = LeaderboardData[j];
I thought this would copy all the data from subscript j to j+1
Then when I subsequently write to the array I (subscript i) I get the correct entry I made, plus a duplicate entry in the adjacent subscript i+1.
When I rewrite the above to:
LeaderboardData[j + 1].UserName = LeaderboardData[j].UserName;
LeaderboardData[j + 1].DateTime = LeaderboardData[j].DateTime;
LeaderboardData[j + 1].Milliseconds = LeaderboardData[j].Milliseconds;
Everything else behaves as expected. So I was wondering exactly what is happening with my first (presumably incorrect) code?
Thanks.
In Java, there's a difference between primitive values and objects (instances of classes): Primitives are stored by value whereas objects are stored by reference. This means that your code would work as you expect if you were using integers. However, since you are using a class, the array merely stores the references to those objects. Hence, when you do LeaderboardData[j + 1] = LeaderboardData[j]; you are merely copying the reference of that object. Therefore, LeaderboardData[j + 1]and LeaderboardData[j] will point to the same object.
Sidenote: If you run your program with a debugger, you can actually see this in action:
The number behind the # denotes the reference number and if you look closely, you can see that the objects at indices 8 and 9 both have the reference #716.
To fix this, I would suggest that you use lists instead of arrays as they allow you to remove and add new entries. The standard list implementation is an ArrayList but in your use-case, a LinkedList might be more efficient.
Lastly, a closing notes on your code: For variable names (like DateTime, UserName or LeaderboardData should always start with a lowercase letter to distinguish them from classes. That way, you can avoid lots of confusion - especially because Java also has a built-in class called DateTime.
Relatively new to programming here so I apologize if this is rather basic.
I am trying to convert string lines into actual variables of different types.
My input is a file in the following format:
double d1, d2 = 3.14, d3;
int a, b = 17, c, g;
global int gInt = 1;
final int fInt = 2;
String s1, s2 = "Still with me?", s3;
These lines are all strings at this point. I wish to extract the variables from the strings and receive the actual variables so I can use and manipulate them.
So far I've tried using regex but I'm stumbling here. Would love some direction as to how this is possible.
I thought of making a general type format for example:
public class IntType{
boolean finalFlag;
boolean globalFlag;
String variableName;
IntType(String variableName, boolean finalFlag, boolean globalFlag){
this.finalflag = finalFlag;
this.globalFlag = globalFlag;
this.variableName = variableName;
}
}
Creating a new wrapper for each of the variable types.
By using and manipulating I would like to then compare between the wrappers I've created and check for duplicate declarations etc'.
But I don't know if I'm on the right path.
Note: Disregard bad format (i.e. no ";" at the end and so on)
While others said that this is not possible, it actually is. However it goes somewhat deep into Java. Just search for java dynamic classloading. For example here:
Method to dynamically load java class files
It allows you do dynamically load a java file at runtime. However your current input does not look like a java file but it can easily be converted to one by wrapping it with a small wrapper class like:
public class CodeWrapper() {
// Insert code from file here
}
You can do this with easy file or text manipulations before loading the ressource as class.
After you have loaded the class you can access its variables via reflection, for example by
Field[] fields = myClassObject.getClass().getFields();
This allows you to access the visibility modifier, the type of the variable, the name, the content and more.
Of course this approach presumes that your code actually is valid java code.
If it is not and you are trying to confirm if it is, you can try to load it. If it fails, it was non-valid.
I have no experience with Java, but as far as my knowledge serves me, it is not possible to actually create variables using a file in any language. You'll want to create some sort of list object which can hold a variable amount of items of a certain type. Then you can read the values from a file, parse them to the type you want it to be, and then save it to the list of the corresponding type.
EDIT:
If I were you, I would change my file layout if possible. It would then look something like this:
1 2 3 4 //1 int, 2 floats, 3 booleans and 4 strings
53
3.14
2.8272
true
false
false
#etc.
In pseudo code, you would then read it as follows:
string[] input = file.Readline().split(' '); // Read the first line and split on the space character
int[] integers = new int[int.Parse(input[0])] // initialise an array with specefied elements
// Make an array for floats and booleans and strings the same way
while(not file.eof) // While you have not reached the end of the file
{
integers.insert(int.Parse(file.ReadLine())) // parse your values according to the size which was given on the first line of the file
}
If you can not change the file layout, then you'll have to do some smart string splitting to extract the values from the file and then create some sort of dynamic array which resizes as you add more values to it.
MORE EDITS:
Based on your comment:
You'll want to split on the '=' character first. From the first half of the split, you'll want to search for a type and from the second half, you can split again on the ',' to find all the values.
I am writing a program that takes in a file and extracts data from a single string within the file. I run into a problem when I try to separate the substrings in the way that I want. The goal is to separate the larger chunks of the line from other large chunks without separating the smaller chunks within the larger chunk (separated by commas).
An example of the file contents would be this: (Although it is slightly long, the files I have may vary from short lists like this to 50 or even to 100 blocks of item sets)
{"timeStamp":1477474644345,"itemSets":[{"mode":"any","sortrank":4999,"type":"custom","priority":false,"isGlobalForMaps":true,"uid":"LOL_D957E9EC-39E4-943E-C55E-52B63E05D99C","isGlobalForChampions":false,"associatedMaps":[],"associatedChampions":[40],"blocks":[{"type":"starting","items":[{"id":"3303","count":1},{"id":"2031","count":1},{"id":"1082","count":1},{"id":"3340","count":1},{"id":"3363","count":1},{"id":"2043","count":1},{"id":"3364","count":1}]},{"type":"Support Build Items","items":[{"id":"2049","count":1},{"id":"1001","count":1},{"id":"3165","count":1},{"id":"3117","count":1},{"id":"2301","count":1},{"id":"3089","count":1},{"id":"3135","count":1},{"id":"3504","count":1}]},{"type":"AP Build Items","items":[{"id":"3165","count":1},{"id":"3020","count":1},{"id":"3089","count":1},{"id":"3135","count":1},{"id":"3285","count":1},{"id":"3116","count":1}]},{"type":"Other Items (Situational Items)","items":[{"id":"3026","count":1},{"id":"3285","count":1},{"id":"3174","count":1},{"id":"3001","count":1},{"id":"3504","count":1}]}],"title":"Janna Items","map":"any"},{"mode":"any","sortrank":0,"type":"custom","priority":false,"isGlobalForMaps":false,"uid":"LOL_F265D25A-EA44-5B86-E37A-C91BD73ACB4F","isGlobalForChampions":true,"associatedMaps":[10],"associatedChampions":[],"blocks":[{"type":"Searching","items":[{"id":"3508","count":1},{"id":"3031","count":1},{"id":"3124","count":1},{"id":"3072","count":1},{"id":"3078","count":1},{"id":"3089","count":1}]}],"title":"TEST","map":"any"}]}
The code I have attempted to write tries to separate this into meaningful chunks, here is what I have written so far:
cutString = dataFromFile.substring(dataFromFile.indexOf("itemSets\":") + 11, dataFromFile.indexOf("},{"));
stringContinue = dataFromFile.substring(cutString.length());
while(stringContinue.contains("},{"))
{
//Do string manipulation to cut every part and re-attach it, then re-check to find if this ("},{\"id") is not there
if(stringContinue.contains("},{\"id"))
{
//if(stringContinue.equals(anObject))
cutString = cutString + stringContinue.substring(0, stringContinue.indexOf("},{\"id"));
}
else if(stringContinue.contains("},{\"count"))
{
cutString = cutString + stringContinue.substring(0, stringContinue.indexOf("},{\"count"));
}
else if(stringContinue.contains("},{"))
{
cutString = cutString + stringContinue.substring(0, stringContinue.indexOf("},{"));
}
stringContinue = stringContinue.substring(cutString.length());
//Check if we see a string pattern that is the cut off point
//if()
//System.out.println(stringContinue);
System.out.println(cutString);
}
But when I run it, I get an output like this:
{"mode":"any","sortrank":4999,"type":"custom","priority":false,"isGlobalForMaps":true,"uid":"LOL_D957E9EC-39E4-943E-C55E-52B63E05D99C","isGlobalForChampions":false,"associatedMaps":[],"associatedChampions":[40],"blocks":[{"type":"starting","items":[{"id":"3303","count":1arting","items":[{"id":"3303","count":1
The output I want to achieve is this:
{"mode":"any","sortrank":4999,"type":"custom","priority":false,"isGlobalForMaps":true,"uid":"LOL_D957E9EC-39E4-943E-C55E-52B63E05D99C","isGlobalForChampions":false,"associatedMaps":[],"associatedChampions":[40],"blocks":[{"type":"starting","items":[{"id":"3303","count":1},{"id":"2031","count":1},{"id":"1082","count":1},{"id":"3340","count":1},{"id":"3363","count":1},{"id":"2043","count":1},{"id":"3364","count":1}]},{"type":"Support Build Items","items":[{"id":"2049","count":1},{"id":"1001","count":1},{"id":"3165","count":1},{"id":"3117","count":1},{"id":"2301","count":1},{"id":"3089","count":1},{"id":"3135","count":1},{"id":"3504","count":1}]},{"type":"AP Build Items","items":[{"id":"3165","count":1},{"id":"3020","count":1},{"id":"3089","count":1},{"id":"3135","count":1},{"id":"3285","count":1},{"id":"3116","count":1}]},{"type":"Other Items (Situational Items)","items":[{"id":"3026","count":1},{"id":"3285","count":1},{"id":"3174","count":1},{"id":"3001","count":1},{"id":"3504","count":1}]}],"title":"Janna Items","map":"any"}
{"mode":"any","sortrank":0,"type":"custom","priority":false,"isGlobalForMaps":false,"uid":"LOL_F265D25A-EA44-5B86-E37A-C91BD73ACB4F","isGlobalForChampions":true,"associatedMaps":[10],"associatedChampions":[],"blocks":[{"type":"Searching","items":[{"id":"3508","count":1},{"id":"3031","count":1},{"id":"3124","count":1},{"id":"3072","count":1},{"id":"3078","count":1},{"id":"3089","count":1}]}],"title":"TEST","map":"any"}
So then my question is how do I check for the point where I can separate the blocks without getting java to detect the same pattern that it uses to separate the smaller chunks? Basically I am looking for a pattern like this ("},{"), but not this ("},{\"id:") or this ("},{\count:"). Is there any other things that the String Class can offer for functionality that is similar that i am not aware of?
Edit: Although using a json parser would make things easier and convenient for this type of problem, another one rises because it would make the program only take in json files. This question is more for string manipulation and trying to find a part of the string that can separate the large blocks of information without touching or changing (very minimally as possible) the smaller blocks that have the same way of separation. So far regex and splitting strings to be re-attached later seems to be the way to go unless there is a more clear-cut answer.
You could split the string into an array based on regex like this:
//fileString is the String you get from your file
String[] chunksIWant = fileString.split("\\},\\{");
This will return the String array chunksIWant split in the chunks you want. It does get rid of the regex itself, in this case "},{", so if you would need the symbols for some reason you will have to add them back afterwards.
You are getting this data from file in Json format.
So when you get that data on java side use JsonParser to convert data in JsonArray format.
Then you can iterate that JsonArray to get as JsonObject by using String name.
You can use value of JsonObject as required.
I'm parsing a CSV using Processing's Table interface, but some rows are missing some data. I want to pull all the data available into my table, but I'm not sure how to handle the missing data--I keep getting NullPointerException when I loop over the table with dataTable.getInt on the missing values.
I don't have a background in statically typed languages, so I've no idea how to conditionally assign this data short of putting a separate try/catch around each assignment. Surely there's a better way?
Before calling dataTable.getInt method check if dataTable is not null like
if(dataTable != null) {
int my_nt = dataTable.getInt
}
//else skip since it is empty
Since your're using getInt--you should perform a regex search/replace ,<not numeric>, with ,<some int>,. In your case it may be as simple as replacing ,, with ,0,
Also, as Hassan suggests, double check that dataTable is not null.
Ok, so I figured out a way to do this:
First, call dataTable.makeNullEmpty(), which turns all the null values into empty strings.
Then, you can use a pattern like this:
String total_value = dataTable.getString(i, 4);
if(total_value.length() > 0) s.total_value = parseInt(total_value);
and you get assignment only if an int is there to be parsed.