Passing string to float array?

Question

Hi i have a string of numbers and want to put them into a float array so i can access the values.

// this bit works fine, data is split into string array.
String fdata[] = data.split(",");
Float array_f[] = new Float(fdata.length);

// this is the bit which throws an error and causes my app to crash.
for (int i = 0; i < fdata.length; i++){
    float y = Float.parseFloat(fdata[i]);
    array_f[i] = y;
}

The error is a

java nullpointerexception: attempt to invoke virtual method java.lang.string java.lang.split(java.lang.string) on a null object reference.

thanks

adding to this i think i need to explain a bit more, so i provided more code to show what im trying to do.

String data; //does this need to define the number of bytes needed then?

start_Acq.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
    channel_a = String.valueOf(channel_Acq.getSelectedItem());
    Thread thread = new Thread(new Runnable() {
        @Override
        public void run() {
            try {
                connection.start_acquisition(channel_a);
                data = connection.start_acquisition(channel_a);
                connection.stop_acquisition();
            }catch (Exception e ){
                e.printStackTrace();
            }
        }
    });thread.start();

    data_recived.setText(data);
    String fdata[] = data.split(",");
    Float array_f[] = new Float[fdata.length];

    for(int i = 0; i<fdata.length; i++){
        float y = Float.parseFloat(fdata[i]);
        array_f[i] = y;
    }

}
});

data is null, you need to check why.... you just cant split a null string :) — ΦXocę 웃 Пepeúpa ツ, Mar 08 '17 at 13:10
Possible duplicate of [What is a NullPointerException, and how do I fix it?](http://stackoverflow.com/questions/218384/what-is-a-nullpointerexception-and-how-do-i-fix-it) — Krishnanunni P V, Mar 08 '17 at 13:12
@BatuhanCoskun what i dont understand is how it can be null, the value data has stored values, could i just initiate the data variable with any value such as 1 just to define a memory location? the string has about 16384 x32 bytes of data. i literally have no idea what to do haha — RedP, Mar 08 '17 at 14:58

score 3 · Answer 1 · answered Mar 08 '17 at 13:55

3

the problem with your code is the initialization, all you have to do is to use the primitive float instead of Float :

 String data = "123,5468,1,25,36";
    String fdata[] = data.split(",");
    float array_f[] = new float[fdata.length];
    for (int i = 0; i < fdata.length; i++){
        array_f[i] = Float.parseFloat(fdata[i]);
System.out.println(array_f[i]);
}

answered Mar 08 '17 at 13:55

Elias

89
10

@llyasse i am just confusing myself i think, i am still learning. I have updated my question, but say with my global variable data, when initialising do i have to define it with an allocated amount of space for when it receives the data. as it needs store 32 x 16384 bytes. – RedP Mar 08 '17 at 14:22
no you don't have to specify the amount of space but you need to make sure that data is stored inside your "data" variable, as the errors shows you're trying to do a split for a null object ! – Elias Mar 08 '17 at 17:01
@llyasse i think the problem is that the program is moving to fast to complete the previous, for instance it is trying to split the data variable while it is still acquiring the data variable from the DAQ. When breakpoints are added and taken one step at a time it works fine. Any advise – RedP Mar 09 '17 at 09:57
yes i think you should add thread.join() after thread.start(). The join call waits for the thread to terminate before returning. – Elias Mar 09 '17 at 11:53
Yeah it works now doesnt pass a null string. Thanks for your help – RedP Mar 17 '17 at 16:28

score 1 · Answer 2 · 2017-03-08T13:36:20.303

1

First of all the data is null; fix it and try by this

float y = java.lang.Float.parseFloat(fdata[i]);

edited Mar 08 '17 at 13:36

answered Mar 08 '17 at 13:16

score 1 · Answer 3 · answered Mar 08 '17 at 13:24

Your array initialization is wrong, it should be like

Float array_f[] = new Float[fdata.length];

after length you should have a semicolon not ','

for (int i=0; i<fdata.length;i++){

EDIT Try this it will work

String fdata[] = new String[]{"6.5", "8.5"};           //this bit works fine, data is split into string array.
        Float array_f[] = new Float[fdata.length];
        for (int i = 0; i < fdata.length; i++) {          //this is the bit which throws an error and causes my app to crash.
            float y = Float.parseFloat(fdata[i]);
            array_f[i] = y;
        }
        System.out.println(Arrays.asList(array_f));

Akash pasupathi · Answer 4 · 2017-03-08T13:46:43.570

0

use this get string array to string then convert float

 for(int i=0;stringarray.length>i;i++){float_var = Float.valueOf(string_array.get(i)); float_array.add(float_var);}

then add float array

edited Mar 08 '17 at 13:46

answered Mar 08 '17 at 13:32

Akash pasupathi

304
1
14

Passing string to float array?

4 Answers4