We Keep Coding

Resizing an Array with a Dedicated method for upsize and downsizing

I'm fairly new to coding and am struggling with an assignment for my class. The program takes a user input for the size of an Array and prompts the user to enter each value 1 at a time. The array size starts at 3 and if the array needs to be bigger when the array has filled a new array that's 2x size is created and all info is copied into it. I was able to figure out this part but I just can't see what I'm doing wrong in the downsizing part. After the info is copied I have to remove the trailing zeroes. I think I have the downsize method right but I don't know if I'm calling it right
import java.util.Scanner;
public class Lab6 {
public static void main(String args[]) {
int[] myarray = new int[3];
int count = 0;
int limit, limitcount = 1;
Scanner kbd = new Scanner(System.in);
System.out.print("How many values would you like to enter? ");
limit = kbd.nextInt();
while (limitcount <= limit) {
System.out.println("Enter an integer value ");
int input = kbd.nextInt();
limitcount++;
if (count < myarray.length) {
myarray[count] = input;
}
else {
myarray = upsize(myarray);
myarray[count] = input;
}
count++;
}
myarray = downsize(myarray, count)
printArray(myarray);
System.out.println("The amount of values in the arrays that we care about is: " + count);
}
static int[] upsize(int[] array) {
int[] bigger = new int[array.length * 2];
for (int i =0;i<array.length; i++) {
bigger[i] = array[i];
}
return bigger;
}
static void printArray( int[] array ) {
for ( int number : array ) {
System.out.print( number + " ");
}
System.out.println();
}
static int[] downsize(int[] array,int count) {
int[] smaller = new int[count];
for (int i =0; i<count; i++) {
smaller[i] = array[i];
}
return array;
}
}

Giving you a full response rather than a comment since you're new here and I don't want to discourage you with brevity which could be misunderstood.
Not sure what happened to your code when you pasted it in here, you've provided everything but the format is weird (the 'code' bit is missing out a few lines at the top and bottom). Might be one to double-check before posting. After posting, I see that someone else has already edited your code to fix this one.
You're missing a semi-colon. I'm not a fan of handing out answers, so I'll leave you to find it :) If you're running your code in an IDE, it should already be flagging that one up for you. If you're not, why on earth not??? IntelliJ is free, easy to get going with, and incredibly helpful. There are others out there as well which different folk prefer :) An IDE will help you spot all sorts of useful things quickly.
I have now run your code, and you do have a problem! It's in your final method, downsize(). Look very, very carefully at the return statement ;) Your questions suggests you aren't actually sure whether or not this method is right, which makes me wonder: have you actually run this code with different inputs to see what results you get? Please do that.
Style-wise: blank lines between methods would make the code easier to look at, by providing a visual gap between components. Please be consistent with putting your opening { on the same line as the method signature, and with having spaces between items, e.g. for (int i = 0; i < count; i++) rather than for (int i =0; i<count; i++). The compiler couldn't care less, but it is easier for humans to look at and just makes it look like you did care. Always a good thing!
I think it is awesome that you are separating some of the work into smaller methods. Seriously. For extra brownie points, think about how you could move that while() block into its own method, e.g. private int[] getUserData(int numberOfItems, Scanner scanner). Your code is great without this, but the more you learn to write tiny units, the more favours you will be doing your future self.
Has your class looked at unit testing yet? Trust me, if not, when you get to this you will realise just how important point 5 can be. Unit tests will also help a lot with issues such as the one in point 3 above.
Overall, it looks pretty good to me. Keep going!!!

Simple mistake in your downsize method. If you have an IDE like Eclipse, Intellij, etc. you would have seen it flagged right away.
return array; // should return smaller
I have a few suggestions since you mentioned being new to coding.
The "limitcount" variable can be removed and substituted with "count" at every instance. I'll leave it to you to figure that out.
Try using more descriptive and understandable variable names. Other people will read your code (like now) and appreciate it.
Try to use consistent spacing/indentation throughout your code.
Your upsize method can be simplified using a System.arraycopy() call which generally performs better and avoids the need for writing out a for loop. You can rewrite downsize in a similar manner.
static int[] upsize(int[] array) {
int[] bigger = new int[array.length * 2];
System.arraycopy(array, 0, bigger, 0, array.length);
return bigger;
}
Edit: All good points by sunrise above - especially that you've done well given your experience. You should set up an IDE when you have the time, they're simple to use and invaluable. When you do so you should learn to step through a debugger to explore the state of your program over time. In this case you would have noticed that the myarray variable was never reassigned after the downsize() call, quickly leading you to a solution (if you had missed the warning about an unused "smaller" array).

What is the fastest way to retrieve values from String?

During my app development one performance question came to my mind:
I have a lot of lines of data that can looks like that:
!ANG:-0.03,0.14,55.31
!ANG:-0.03,-0.14,305.31
!ANG:-234.03,-0.14,55.31
in general: !ANG:float,float,float
Between those lines there are also "damaged" lines - they don't start with ! or are too short/have extra signs and so on.
To detect lines that are damaged at the begining I simply use
if(myString.charAt(0) != '!')//wrong string
What I can do to detect lines that are damaged at the end? It is very important to mention that I need not only to check if the line is correct but also get those 3 float numbers to use it later.
I've found three options for this:
use regexp
split twice (first ":" and second ",") and count elements
use Scanner class
I am not sure which one of this (or maybe there are other) methods will be the best from the performance point of view. Can you please give me some advice?
EDIT:
After some comments I see that it is worth to write how damage lines an look:
NG:-0.03,0.14,55.31
.14,55.31
!ANG:-0.03,0.14,
!A,-0.02,-0.14,554,-0.12,55
It is quite difficult to talk about number of lines because I am getting them from readings from other device so I get packets of around 20 lines at a time with a frequency of 50Hz.
What I've found out so far is the big drawback of using scanner - for each line I need to create new object and after some time my device is starting to get short on resources.

Benchmark them, then you will know.
The likely fastest way is to write your own tiny state machine to match your format and find the float boundaries. Theoretically a regex will have the same performance, but it's likely to have additional overhead.

As an intermediate solution I'd do something like that :
private static class LineObject {
private float f1, f2, f3;
}
private LineObject parseLine(String line) {
LineObject obj = null;
if (line.startsWith("!ANG:")) {
int i = line.indexOf(',', 5);
if (i != -1) {
int j = line.indexOf(',', i+1);
if (j != -1) {
try {
obj = new LineObject();
obj.f1 = Float.parseFloat(line.substring(5, i));
obj.f2 = Float.parseFloat(line.substring(i+1, j));
obj.f3 = Float.parseFloat(line.substring(++j));
} catch (NumberFormatException e) {
return null;
}
}
}
}
return obj;
}
After you can copy/paste only usefull jdk code of startsWith, indexOf and parseFloat in your own state machine...

WeibullGen Parameters using umontreal.iro.lecuyer.randvar package java

I am trying to generate weibull random numbers using WeibullGen from umontreal.iro.lecuyer.randvar package this is my code
RandomStream stream = new MRG32k3a();
for(int i=0;i<5;i++) {
int result = WeibullGen.nextDouble(stream, alp, lam,bet);
System.out.println(result);
}
But I am a little confused about the parameters I mean does lam means the scale or the rate parameters, I think alp means the shape parameter. finally, I am confused about the last parameter bet what it present. I tried to look online but it wasn't clear to me.
Thanks in advance

Printing individual parts of an array in a Java Gui app

OK, so I created a console app that, among other things, takes an array of numbers and prints them out one by one, line by line. Now, I have to take the class that I created for that console app, and pop it into a separate GUI app we're creating. I have all of the other methods working fine, but for the life of me I cannot get the array method to print out correctly. It just gives me the last number I typed into the text field. I'm hoping someone can give me a nudge to help me figure this part out so I can move along, and get to the whole SpringLayout stuff, (the main part of the new assignment) I am limited in what I can show you here because this is a current assignment, so I will have to stick to this stuff as specifically as I can. And please, don't just post the code as an answer, (because then I can't use it), thanks.
Here's what I had for my original project for the array method:
int [] getArray(int x)
{
breakUpNum(x);
return numAry;
}
From there, inside my new class I have this, in an attempt to get it to print:
private class ButtonTest implements ActionListener
{
public void actionPerformed(ActionEvent ae)
{
Lab1 tester = new Lab1();
int[] test4 = tester.getArray(num);
for(int i = 0; i < test4.length; i ++)
{
crossTest.getArrCross.setText("" + test4[i]);
}
}
}
Any help pointing me in the right direction would be greatly appreciated, thanks!

setText does just that, sets the text you pass to as the current text content, it does not append it.
If you were to use JTextArea, you could use it's append method...however, for a JTextField you need to have a different approach.
Now you could use getArrCross.setText(getArrCross.getText() + test4[i])...but to quite frank, that's rather inefficient, as each call to setText is going to stage a paint event...
StringBuilder sb = new StringBuilder(128);
for(int i = 0; i < test4.length; i ++)
{
sb.append(test4[i]);
}
crossTest.getArrCross.setText(sb.toString());
Now, if you want to separate each element, you need to add
if (sb.length() > 0) {
sb.append(", ");
}
Before sb.append(test4[i]);

The last bit of actionPerformed in the for loop isn't working right. setText replaces the current text with its argument, and it doesn't seem like you want to do that. To fix it, replace the line in the for loop with this:
crossTest.getArrCross.setText(crossTest.getArrCross.getText() + test4[i]);

Making an animated underscore in java

Its not really an animation, but I want it so i have a flashing underscore next to my text. I want this to simulate that more text can be entered..
e.g. one second its '_' and the other second its gone..
Thanks :D
ps I tried an idea where i had a while(flashing) loop and in there i made a string equal '_' and then made it equal '' but that didnt work..
while(flashing) {
s = "_";
s = "";
}
Thanks for the help in advance!
EDIT:::
This is how i am displaying the string in the game:
drawCenteredString(fontRenderer, "Missile Command Center" + s, width / 2, 40, 0xffffff);

Like #Vulcan said, you actually can't do this with a while loop. You have to 'redraw' the centeredString every second or so, once with an underscore and next time without the underscore

You didn't tell us what kind of graphic libraries you are using.
If you want to do something like a flashing underscore there are two ways, one can be very bad, the second can be better.
The first one is something just like (pseudocoded):
while(flashing){
textView.setText(textView.getText()+"_"); // I am assuming that you are using a text view, take this as pseudocode, you can do to whatever you want.
sleep(500); //that is half a second
textView.setText(textView.getText().substr(0,textView.getText().length()-1));
sleep(500);
}
The second is better.
I assume you are using something like OpenGL to draw the graphics (as minecraft do, if I remember well).
private long timePassed = 0;
public void draw(long delta){
timePassed += delta;
String t = textView.getText();
if(timepassed > blinkingSpeed){
timepassed = 0;
if("_".equals(t.substr(t.length()-1,t.length()))){
//The last char is the underscore, i remove it.
textView.setText(t.substr(0,t.length()-1));
}else{
//The last char isn't an underscore. I add it.
textView.setText(t + "_");
}
}
delta is a difference between the last time we done a loop and the actual time.
so when calling draw method you should have something like this
//metod where draw is called
delta = Sys.getTimer() - lastTimerGotten;
lastTimerGotten = Sys.getTimer();
draw(delta);
//etc etc
Obviously each frame rendering you should call the draw(long delta) method.
I hope you understand what I am trying to explain you.
There is no way to make what you first wrote work.