Develop Reference

Is there a way to select specific characters from a TextView variable?

I am using AWS IoT to read and publish some information from a microelectronic's sensors. I am able to get the json file in the app as a big wall of text, but it is not very readable. I am using TextView as I don't want the user to be able to change the information. My problem is that I can't find a way to remove the parts that are not necessary to the user.
I am new to app creation, so I am trying to do this as simply as possible. I have my xml ready to receive the information; I just need the info in a variable that I can pass to it. I have tried implementing a character array, but haven't been able to get past the fact that I can't edit the text view.
tvLastMessage = (TextView) findViewById(R.id.tvLastMessage);
This is currently the block of text that I am receiving. It looks like this:
{"sensors":[{"name":"steamTemp","data":"181.39","state":1,
{"name":"waterTemp","data":"-713.15","state":0,
{"name":"waterFlow","data":"0.00","state":3,
{"name":"dieselFlow","data":"0.00","state":2,
{"name":"manualResetLevel","data":"1","state":0,
{"name":"waterFeederLevel","data":"1","state":0,
{"name":"autoResetPressure","data":"1","state":0,
{"name":"manualResetPressure","data":"1","state":0},
{"name":"tempLimit","data":"1","state":0,
{"name":"heatEff","data":"0.00","state":2}]}
The text does not look as formatted as this, but it is more understandable and readable to represent it this way. It normally does not have the new lines, so it will just naturally go to one as it runs out of room.
I am hoping that I can get it to simply show the numbers associated with each "name" and "data" as I have those hard-coded into my xml since they don't change. Just getting those numbers into different variables would be ideal, so I can simply reference the variable in my xml file. However, if there is a better way to do this, I am happy to take suggestions!

Try using a loop to find each instance of "name", "data", and "state", and get the values between them.
Assuming input is a string:
String string = "{\"sensors\":[{\"name\":\"steamTemp\",\"data\":\"181.39\",\"state\":1,\n{\"name\":\"waterTemp\",\"data\":\"-713.15\",\"state\":0,\n{\"name\":\"waterFlow\",\"data\":\"0.00\",\"state\":3,\n{\"name\":\"dieselFlow\",\"data\":\"0.00\",\"state\":2,\n{\"name\":\"manualResetLevel\",\"data\":\"1\",\"state\":0,\n{\"name\":\"waterFeederLevel\",\"data\":\"1\",\"state\":0,\n{\"name\":\"autoResetPressure\",\"data\":\"1\",\"state\":0,\n{\"name\":\"manualResetPressure\",\"data\":\"1\",\"state\":0},\n{\"name\":\"tempLimit\",\"data\":\"1\",\"state\":0,\n{\"name\":\"heatEff\",\"data\":\"0.00\",\"state\":2}]}";
Map<String, Double> map = new HashMap<>();
int index0 = 0, index1, index2;
while (true) {
// Get indices
index0 = string.indexOf("name", index0);
index1 = string.indexOf("data", index0);
index2 = string.indexOf("state", index1);
// If "name", "data", or "state" was not found
if (index0 == -1 || index1 == -1 || index2 == -1)
break;
// Get the data from the string and put it into the map
String key = string.substring(index0 + 7, index1 - 3);
Double value = Double.parseDouble(string.substring(index1 + 7, index2 - 3));
map.put(key, value);
// Update index
index0 = index2;
}
System.out.println(map);
Output:
{waterFlow=0.0, manualResetLevel=1.0, waterFeederLevel=1.0, manualResetPressure=1.0, waterTemp=-713.15, autoResetPressure=1.0, tempLimit=1.0, dieselFlow=0.0, heatEff=0.0, steamTemp=181.39}

Subtraction in Java value shortage

I encounter a difficult problem. I am looking for a suggestion how to approach in this problem. I have three field in my dataset. I want to perform a subtraction.The problem is like that.
Time(s) a x
1 0.1 0.2
2 0.4
3 0.6
4 0.7
5 0.2 0.9
I need to perform a subtraction from (a-x). But the method of subtraction is like that at time 1s a has value 0.1. The operation will be (0.1-0.2) 1st iteration. 2nd iteration (0.1-0.4). 3rd iteration (0.1-0.6).4th iteration (0.1-0.7) But in 2nd iteration it will be (0.2-0.9).
This is my problem statement. I want to write down this code in Java. I don't need Java code. I can write it down myself. I need a suggestion how to proceed in this approach?. One thought is that creating array for each variable. But then stuck on loop. How the loop iterated? It is clear array a is static until it get next value, which is available at Time 5s.

This will depend on how large is your input file:
If the dataset fits into memory load it as either 2 separate array or as one array of Row objects with a and x as fields. After that it's simple iteration remembering what was the last row that contained a to use it when a is missing.
If the dataset is large it's better to read it using BufferedReader and only remember the last encountered a and x. This will greatly reduce the memory consumption and would be the preferred approach.

If a changes every 4 numbers you can use time's / 4 + 1 to get value from small array of a.
If a changes not every 4 numbers, then I suggest to use full array filled with same values.

Now that I see you're not using a database and just reading from a file, maybe try this
Just keep the old value of a until a new value can overwrite it.
This is memory efficient since it parses line by line.
public static List<Double> parseFile(String myFile) throws IOException {
List<Double> results = new ArrayList<>();
try (BufferedReader b = new BufferedReader(new FileReader(myFile));) {
b.readLine(); // ** skip header?
String line;
Integer time = null;
Double a = null;
Double x = null;
for (int lineNum = 0; (line = b.readLine()) != null; lineNum++) {
// ** split the data on any-and-all-whitespace
final String[] data = line.split("\\s+");
if (data.length != 3)
throw new RuntimeException("Invalid data format on line " + lineNum);
try {
time = Integer.valueOf(data[0]);
if (!data[1].trim().isEmpty()) {
a = Double.valueOf(data[1]);
}
if (!data[2].trim().isEmpty()) {
x = Double.valueOf(data[2]);
}
} catch (Exception e) {
throw new RuntimeException("Couldn't parse line " + lineNum, e);
}
if (a == null || x == null) {
throw new RuntimeException("Values not initialized at line " + lineNum);
}
results.add(Double.valueOf(a.doubleValue() - x.doubleValue()));
}
}
// ** finished parsing file, return results
return results;
}

ArrayList for java

So, this is my question that I have to answer:
In the Payroll class, add a method with the header private int
computePay(Programmer p). The method should return the programmer’s
grade multiplied by the number of hours they worked. For example, if
the programmer’s grade is 2, and the total hours they worked is 6, the
method should return 12.
But my question for this forum is, how do I get a txt. file which contains Firstname Secondname,paygrade(Out of 3),hours,hours,hours,hours,hours,hours
(txt. example;
Sean Dyke,3,34,54,67,78,34,12
Fred Flintsone,1,65,78,89,89,34,23
Scooby Doo,2,54,56,67,87,89,65
)
To make the grade part separate to the hours they work, so I can then use
private int computePay(Programmer p){
return p.grade*p.hours;
}
I may have confused myself in this one, or thinking backwards, but any sort of guidelines would help.

I think the grade is after the name so you can split the array and take the values.
String[] temp = array1.split(",");
temp[0] gives name
temp[1] gives grade
temp[2...] gives hours worked

Well there are 2 ways of storing data in a .txt file:
You can put your object into an object stream and simply write that into a textfile.
FileOutputStream out = new FileOutputStream("test.txt");
ObjectOutputStream oout = new ObjectOutputStream(out);
// write something in the file
oout.writeObject(s);
// close the stream
oout.close();
Sadly the formating would be really bad and you could not read data on your own. Also that method is really inconsistent. You would need your class to implement Serializable. Furthmore, any change in your java code would stop making it possible to read that file.
So I would go for an attampt where you just store the name, followed by those hours. Then, read it line by line:
String s = "Sean Dyke,3,34,54,67,78,34,12"
String[] entries = s.split(",");
String name = entries[0];
Integer[] hours = new Integer[entries.length -1];
for(int i = 0; i < hours; i++){
hours[i] = Integer.parseInt(entries[i + 1]);
}
This could would parse one line. Do it for every line in your code txt file and you should be fine.

what is the fastest way to get dimensions of a csv file in java

My regular procedure when coming to the task on getting dimensions of a csv file as following:
Get how many rows it has:
I use a while loop to read every lines and count up through each successful read. The cons is that it takes time to read the whole file just to count how many rows it has.
then get how many columns it has:
I use String[] temp = lineOfText.split(","); and then take the size of temp.
Is there any smarter method? Like:
file1 = read.csv;
xDimention = file1.xDimention;
yDimention = file1.yDimention;

I guess it depends on how regular the structure is, and whether you need an exact answer or not.
I could imagine looking at the first few rows (or randomly skipping through the file), and then dividing the file size by average row size to determine a rough row count.
If you control how these files get written, you could potentially tag them or add a metadata file next to them containing row counts.
Strictly speaking, the way you're splitting the line doesn't cover all possible cases. "hello, world", 4, 5 should read as having 3 columns, not 4.

Your approach won't work with multi-line values (you'll get an invalid number of rows) and quoted values that might happen to contain the deliminter (you'll get an invalid number of columns).
You should use a CSV parser such as the one provided by univocity-parsers.
Using the uniVocity CSV parser, that fastest way to determine the dimensions would be with the following code. It parses a 150MB file to give its dimensions in 1.2 seconds:
// Let's create our own RowProcessor to analyze the rows
static class CsvDimension extends AbstractRowProcessor {
int lastColumn = -1;
long rowCount = 0;
#Override
public void rowProcessed(String[] row, ParsingContext context) {
rowCount++;
if (lastColumn < row.length) {
lastColumn = row.length;
}
}
}
public static void main(String... args) throws FileNotFoundException {
// let's measure the time roughly
long start = System.currentTimeMillis();
//Creates an instance of our own custom RowProcessor, defined above.
CsvDimension myDimensionProcessor = new CsvDimension();
CsvParserSettings settings = new CsvParserSettings();
//This tells the parser that no row should have more than 2,000,000 columns
settings.setMaxColumns(2000000);
//Here you can select the column indexes you are interested in reading.
//The parser will return values for the columns you selected, in the order you defined
//By selecting no indexes here, no String objects will be created
settings.selectIndexes(/*nothing here*/);
//When you select indexes, the columns are reordered so they come in the order you defined.
//By disabling column reordering, you will get the original row, with nulls in the columns you didn't select
settings.setColumnReorderingEnabled(false);
//We instruct the parser to send all rows parsed to your custom RowProcessor.
settings.setRowProcessor(myDimensionProcessor);
//Finally, we create a parser
CsvParser parser = new CsvParser(settings);
//And parse! All rows are sent to your custom RowProcessor (CsvDimension)
//I'm using a 150MB CSV file with 1.3 million rows.
parser.parse(new FileReader(new File("c:/tmp/worldcitiespop.txt")));
//Nothing else to do. The parser closes the input and does everything for you safely. Let's just get the results:
System.out.println("Columns: " + myDimensionProcessor.lastColumn);
System.out.println("Rows: " + myDimensionProcessor.rowCount);
System.out.println("Time taken: " + (System.currentTimeMillis() - start) + " ms");
}
The output will be:
Columns: 7
Rows: 3173959
Time taken: 1279 ms
Disclosure: I am the author of this library. It's open-source and free (Apache V2.0 license).

IMO, What you are doing is an acceptable way to do it. But here are some ways you could make it faster:
Rather than reading lines, which creates a new String Object for each line, just use String.indexOf to find the bounds of your lines
Rather than using line.split, again use indexOf to count the number of commas
Multithreading

I guess here are the options which will depend on how you use the data:
Store dimensions of your csv file when writing the file (in the first row or as in an additional file)
Use a more efficient way to count lines - maybe http://docs.oracle.com/javase/6/docs/api/java/io/LineNumberReader.html
Instead of creating an arrays of fixed size (assuming thats what you need the line count for) use array lists - this may or may not be more efficient depending on size of file.

To find number of rows you have to read the whole file. There is nothing you can do here. However your method of finding number of cols is a bit inefficient. Instead of split just count how many times "," appeard in the line. You might also include here special condition about fields put in the quotas as mentioned by #Vlad.
String.split method creates an array of strings as a result and splits using regexp which is not very efficient.

I find this short but interesting solution here:
https://stackoverflow.com/a/5342096/4082824
LineNumberReader lnr = new LineNumberReader(new FileReader(new File("File1")));
lnr.skip(Long.MAX_VALUE);
System.out.println(lnr.getLineNumber() + 1); //Add 1 because line index starts at 0
lnr.close();

My solution is simply and correctly process CSV with multiline cells or quoted values.
for example We have csv-file:
1,"""2""","""111,222""","""234;222""","""""","1
2
3"
2,"""2""","""111,222""","""234;222""","""""","2
3"
3,"""5""","""1112""","""10;2""","""""","1
2"
And my solution snippet is:
import java.io.*;
public class CsvDimension {
public void parse(Reader reader) throws IOException {
long cells = 0;
int lines = 0;
int c;
boolean qouted = false;
while ((c = reader.read()) != -1) {
if (c == '"') {
qouted = !qouted;
}
if (!qouted) {
if (c == '\n') {
lines++;
cells++;
}
if (c == ',') {
cells++;
}
}
}
System.out.printf("lines : %d\n cells %d\n cols: %d\n", lines, cells, cells / lines);
reader.close();
}
public static void main(String args[]) throws IOException {
new CsvDimension().parse(new BufferedReader(new FileReader(new File("test.csv"))));
}
}

Null Pointer that makes no sense to me?

Im currently working on a program and any time i call Products[1] there is no null pointer error however, when i call Products[0] or Products[2] i get a null pointer error. However i am still getting 2 different outputs almost like there is a [0] and 1 or 1 and 2 in the array. Here is my code
FileReader file = new FileReader(location);
BufferedReader reader = new BufferedReader(file);
int numberOfLines = readLines();
String [] data = new String[numberOfLines];
Products = new Product[numberOfLines];
calc = new Calculator();
int prod_count = 0;
for(int i = 0; i < numberOfLines; i++)
{
data = reader.readLine().split("(?<=\\d)\\s+|\\s+at\\s+");
if(data[i].contains("input"))
{
continue;
}
Products[prod_count] = new Product();
Products[prod_count].setName(data[1]);
System.out.println(Products[prod_count].getName());
BigDecimal price = new BigDecimal(data[2]);
Products[prod_count].setPrice(price);
for(String dataSt : data)
{
if(dataSt.toLowerCase().contains("imported"))
{
Products[prod_count].setImported(true);
}
else{
Products[prod_count].setImported(false);
}
}
calc.calculateTax(Products[prod_count]);
calc.calculateItemTotal(Products[prod_count]);
prod_count++;
This is the output :
imported box of chocolates
1.50
11.50
imported bottle of perfume
7.12
54.62
This print works System.out.println(Products[1].getProductTotal());
This becomes a null pointer System.out.println(Products[2].getProductTotal());
This also becomes a null pointer System.out.println(Products[0].getProductTotal());

You're skipping lines containing "input".
if(data[i].contains("input")) {
continue; // Products[i] will be null
}
Probably it would be better to make products an ArrayList, and add only the meaningful rows to it.
products should also start with lowercase to follow Java conventions. Types start with uppercase, parameters & variables start with lowercase. Not all Java coding conventions are perfect -- but this one's very useful.
The code is otherwise structured fine, but arrays are not a very flexible type to build from program logic (since the length has to be pre-determined, skipping requires you to keep track of the index, and it can't track the size as you build it).
Generally you should build List (ArrayList). Map (HashMap, LinkedHashMap, TreeMap) and Set (HashSet) can be useful too.
Second bug: as Bohemian says: in data[] you've confused the concepts of a list of all lines, and data[] being the tokens parsed/ split from a single line.
"data" is generally a meaningless term. Use meaningful terms/names & your programs are far less likely to have bugs in them.
You should probably just use tokens for the line tokens, not declare it outside/ before it is needed, and not try to index it by line -- because, quite simply, there should be absolutely no need to.
for(int i = 0; i < numberOfLines; i++) {
// we shouldn't need data[] for all lines, and we weren't using it as such.
String line = reader.readLine();
String[] tokens = line.split("(?<=\\d)\\s+|\\s+at\\s+");
//
if (tokens[0].equals("input")) { // unclear which you actually mean.
/* if (line.contains("input")) { */
continue;
}
When you offer sample input for a question, edit it into the body of the question so it's readable. Putting it in the comments, where it can't be read properly, is just wasting the time of people who are trying to help you.

Bug alert: You are overwriting data:
String [] data = new String[numberOfLines];
then in the loop:
data = reader.readLine().split("(?<=\\d)\\s+|\\s+at\\s+");
So who knows how large it is - depends on the success of the split - but your code relies on it being numberOfLines long.

You need to use different indexes for the line number and the new product objects. If you have 20 lines but 5 of them are "input" then you only have 15 new product objects.
For example:
int prod_count = 0;
for (int i = 0; i < numberOfLines; i++)
{
data = reader.readLine().split("(?<=\\d)\\s+|\\s+at\\s+");
if (data[i].contains("input"))
{
continue;
}
Products[prod_count] = new Product();
Products[prod_count].setName(data[1]);
// etc.
prod_count++; // last thing to do
}