I got this code that fetches floats from a database.
for (int i = 0; i < ingredient.size() ; i++) {
Ingredient ing = (Ingredient) ingredient.get(i);
ingredients += String.valueOf(ing.getAmount()) + " " +
ing.getUnit() + " " + ing.getIngredient() + "\n";
}
The database is written in REAL values as some of them is 1.5, 2.5, 1.4 etc. But we also have these whole numbers without the need of a decimal, such as 1, 4, 10 etc.
The problem is that the database table needs to be in REAL value, which gives us no choice but to give all the values one decimal, no matter if it's needed or not.
So we'll end up with values like:
1.0
1.5
2.3
20.0
5.0
My question is: How do we remove the unnecessary decimals, but keep the ones that need it?
One very simple way to remove these would be to strip the characters using StringUtils.
String displayValue = String.valueOf(ing.getAmount());
displayValue = StringUtils.stripEnd(displayValue, ".0");
For an input of "1.0", "1" will be returned.
A more technical approach would be to use the modulus operator %
For example:
if(value%1 == 0){ //1 divides into number perfectly, there is no decimal
//cast value to integer or another non decimal variable
} else {
//use existing value as it contains a decimal
}
How about this (does't require any fancy things like StringUtils)?
String s = String.valueOf(1.0);
System.out.println(s);
/* Make this block as a function and return an int */
String ss = " ";
if (s.charAt(s.length()-2) == '.' && s.charAt(s.length()-1) == '0'){
ss = s.substring(0,s.length()-2);
System.out.println(ss);
}
/**************************************************/
int converted = Integer.parseInt(ss);
System.out.println(converted);
}
If you want to make it a function block, you can.
You can check it working on IDEONE - http://ideone.com/udJv8M
Check the float values with modulo. If 0 is returned it is an Integer. Here is an example with the numbers you have mentioned:
List<Float> values = new ArrayList<Float>();
values.add(new Float(1.0f));
values.add(new Float(1.5f));
values.add(new Float(2.3f));
values.add(new Float(20.0f));
values.add(new Float(5.0f));
List<String> strValues = new ArrayList<String>();
for(Float value : values)
{
String strValue = "";
if(value % 1 == 0)
{
Integer intValue = value.intValue();
strValue = intValue.toString();
strValues.add(strValue);
}
else
{
strValue = value.toString();
strValues.add(strValue);
}
System.out.println(strValue);
}
You can use a custom DecimalFormat pattern:
public static String customFormat(String pattern, double value) {
DecimalFormat myFormatter = new DecimalFormat(pattern);
return myFormatter.format(value);
}
Then a pattern of # defines places holders for optional digits, so #.### will give up to 3 digits where necessary only.
for (int i = 0; i < ingredient.size() ; i++) {
Ingredient ing = (Ingredient) ingredient.get(i);
ingredients += customFormat("#.###", ing.getAmount()) +
" " + ing.getUnit() + " " + ing.getIngredient() + "\n";
}
So don't convert your data to a String except for display only. Real numbers can represent both integers and floating point numbers using the same data type. Plus if you ever needed to do any math on your numbers you can't use Strings to do that. If you convert your numbers from the database directly to String before storing them into Ingredient then you've screwed yourself later on if you want to do calculations on those numbers. (Say you wanted to add a feature to double a recipe and have all of the quantities change for the user). Under your current plan you're preventing yourself from doing something like that because you're overly focused on the display of that number.
Instead just create a method on Ingredient to convert your numbers using String.format(). Like so:
public class Ingredient {
private double amount;
private String name;
public String asDecimal() {
return String.format("%.1f", amount);
}
public String asInteger() {
return String.format("%.0f", amount);
}
public String asFraction() {
// exercise left to the reader
}
}
You could even add a function that converts decimals to fractional amounts to make it easier to display things chiefs might understand vs decimals which are harder. Bear in mind String.format() will round floating point amounts (0.5 -> 1 using as Integer).
Convert your String returned from ing.getAmount() to a Float object, then use the modulo function to determine whether your value is an exact multiple of 1 (ie no decimal places). If so, convert your Float object to an int, which will concatenate the decimals.
Float f = Float.valueOf(ing.getAmount());
if(f%1 == 0) {
// Use f.intValue() to concatenate your decimals.
ingredients +=String.valueOf(f.intValue() + " " + ing.getUnit() + " " + ing.getIngredient() + "\n";
}
else {
ingredients +=String.valueOf(ing.getAmount()) + " " + ing.getUnit() + " " + ing.getIngredient() + "\n";
}
I hope this helps.
Related
Attempting to convert string of numbers to binary with this code
public static int convert(String text)
{
int num =0;
for(int i =0; i<text.length();i++)
{
if(((int)text.charAt(i)>=48)&&((int)text.charAt(i)<=59))
{
System.out.println("Before: i = " + i + " num = "+ num+" char = "+ text.charAt(i) + "numchar = " + ((int)text.charAt(i)-48));
num = num*10 + ((int)text.charAt(i)-48);
System.out.println("After: i = " + i + " num = "+ num+" char = "+ text.charAt(i) + "numchar = " + ((int)text.charAt(i)-48));
}
}
return num;
}
}
However once it reaches its 10th number the output becomes a complete jumble with negative numbers and random numbers, even when my test strings are binary. Any idea why this could be happening?
The int datatype in Java is a 32-bit signed integer, so the maximum value it can represent is 2^31 - 1 = 2147483647. Since you are trying to parse numbers bigger than this, your arithmetic will result in integer overflow.
To solve this problem you will need to use a datatype which can represent larger integers, such as long (up to about 19 digits) or BigInteger (arbitrarily large).
I am trying to figure out how to find the percent difference between the original (no space) string of text and the disemvoweled (no space) string of text. I am attempting to do this by using the equation ((newAmount-reducedAmount)/reducedAmount) but I am having no luck and am ending up with a value of zero, as shown below.
Thank you!
My Code:
import java.util.Scanner;
public class Prog5 {
public static void main(String[] args) {
// TODO Auto-generated method stub
Scanner console = new Scanner(System.in);
System.out.println("Welcome to the disemvoweling utility!"); // Initially typed "disemboweling" xD
System.out.print("Enter text to be disemvoweled: ");
String inLine = console.nextLine();
String vowels= inLine.replaceAll("[AEIOUaeiou]", ""); // RegEx for vowel control
System.out.println("Your disemvoweled text is: " + vowels); // Prints disemvoweled text
// Used to count all characters without counting white space(s)
int reducedAmount = 0;
for (int i = 0, length = inLine.length(); i < length; i++) {
if (inLine.charAt(i) != ' ') {
reducedAmount++;
}
}
// newAmount is the number of characters on the disemvoweled text without counting white space(s)
int newAmount = 0;
for (int i = 0, length = vowels.length(); i < length; i++) {
if (vowels.charAt(i) != ' ') {
newAmount++;
}
}
int reductionRate = ((newAmount - reducedAmount) / reducedAmount); // Percentage of character reduction
System.out.print("Reduced from " + reducedAmount + " to " + newAmount + ". Reduction rate is " + reductionRate + "%");
}
}
My output: (Test string is without quotes: "Testing please")
Welcome to the disemvoweling utility!
Enter text to be disemvoweled: Testing please
Your disemvoweled text is: Tstng pls
Reduced from 13 to 8. Reduction rate is 0%
You used an integer data type while calculating percentage difference while performing integer division. You need to type cast one of the variables on the right hand side of the equation to perform double division and then store them in double. The reason for doing this is java integer type can't hold the real numbers.
Also, multiple it by 100 to get the percentage.
double reductionRate = 100 * ((newAmount - reducedAmount) / (double)reducedAmount);
If you want a fraction between 0 and 1, then
double reductionRate = ((newAmount - reducedAmount) / (double)reducedAmount);
Your formula gives you a value between zero and one.
An integer cannot hold fractions so it always shows zero.
Multiply by 100 to get a regular percentage value.
int reductionRate = 100*(newAmount - reducedAmount) / reducedAmount; // Percentage of character reduction
My app lets users search a location and one of the queries I got was
"78°14'09"N 15°29'29"E"
Obviously the user wants to go to this location.
First how do I check if this string fits the decimal format correctly. Then how do I convert it to double format?
double latitude = convertToDouble("78°14'09"N")
I searched here on stackoverflow but they are all looking for the opposite: double to decimal.
78°14'09"N 15°29'29"E
First how do I check if this string fits the decimal format correctly. Then how do I convert it to double format?
The string is not in decimal (degrees) format. It is in degrees, minutes, and seconds, which is more or less the opposite of decimal degrees format. I therefore interpret you to mean that you want to test whether the string is in valid D/M/S format, and if so, to convert it to decimal degrees, represented as a pair of doubles.
This is mostly a parsing problem, and regular expressions are often useful for simple parsing problems such as this one. A suitable regular expression can both check the format and capture the numeric parts that you need to extract. Here is one way to create such a pattern:
private final static Pattern DMS_PATTERN = Pattern.compile(
"(-?)([0-9]{1,2})°([0-5]?[0-9])'([0-5]?[0-9])\"([NS])\\s*" +
"(-?)([0-1]?[0-9]{1,2})°([0-5]?[0-9])'([0-5]?[0-9])\"([EW])");
That's a bit dense, I acknowledge. If you are not familiar with regular expressions then this is no place for a complete explanation; the API docs for Pattern provide an overview, and you can find tutorials in many places. If you find that your input matches this pattern, then not only have you verified the format, but you have also parsed out the correct pieces for the conversion to decimal degrees.
The basic formula is decimal = degrees + minutes / 60 + seconds / 3600. You have the additional complication that coordinates' direction from the equator / prime meridian might be expressed either via N/S, E/W or by signed N, E, or by a combination of both. The above pattern accommodates all of those alternatives.
Putting it all together, you might do something like this:
private double toDouble(Matcher m, int offset) {
int sign = "".equals(m.group(1 + offset)) ? 1 : -1;
double degrees = Double.parseDouble(m.group(2 + offset));
double minutes = Double.parseDouble(m.group(3 + offset));
double seconds = Double.parseDouble(m.group(4 + offset));
int direction = "NE".contains(m.group(5 + offset)) ? 1 : -1;
return sign * direction * (degrees + minutes / 60 + seconds / 3600);
}
public double[] convert(String dms) {
Matcher m = DMS_PATTERN.matcher(dms.trim());
if (m.matches()) {
double latitude = toDouble(m, 0);
double longitude = toDouble(m, 5);
if ((Math.abs(latitude) > 90) || (Math.abs(longitude) > 180)) {
throw new NumberFormatException("Invalid latitude or longitude");
}
return new double[] { latitude, longitude };
} else {
throw new NumberFormatException(
"Malformed degrees/minutes/seconds/direction coordinates");
}
}
The convert() method is the main one; it returns the coordinates as an array of two doubles, representing the coordinates in decimal degrees north and east of the intersection of the equator with the prime meridian. Latitudes south of the equator are represented as negative, as are longitudes west of the prime meridian. A NumberFormatException is thrown if the input does not match the pattern, or if the latitude or longitude apparently represented is invalid (the magnitude of the longitude cannot exceed 180°; that of the latitude cannot exceed 90°).
You won't be able to parse that into a double without removing the non number chars but,
String string = "78°14'09"N";
Double number = 0;
try{
number = Double.parseDouble(string);
//do something..
}catch (NumberFormatException e){
//do something.. can't be parsed
}
If you first remove any characters from the string that are not alphanumeric, then something along these lines will work. This code compiles.
public class HelloWorld{
public static void main(String []args){
String input = "78 14'09 N 15 29'29 E".replaceAll("[^A-Za-z0-9]", " ");
String[] array = input.split(" ");
int nDegree = Integer.parseInt(array[0]);
int nMinute = Integer.parseInt(array[1]);
int nSecond = Integer.parseInt(array[2]);
int eDegree = Integer.parseInt(array[4]);
int eMinute = Integer.parseInt(array[5]);
int eSecond = Integer.parseInt(array[6]);
double nDegrees = nDegree + (double) nMinute/60 + (double) nSecond/3600;
double eDegrees = eDegree + (double) eMinute/60 + (double) eSecond/3600;
String nResult = "Decimal = N " + Double.toString(nDegrees).substring(0,10);
String eResult = "Decimal = E " + Double.toString(eDegrees).substring(0,10);
System.out.println(nResult);
System.out.println(eResult);
}
}
Output:
Decimal = N 78.2358333
Decimal = E 15.4913888
The problem is that Java can't store the degrees ° character as part of a String, or internal quotes (the minute character). If you can find a way to remove them from the string before inputting the data, then this will work.
I don't have a solution for handling the degrees symbol, but you could use an escape symbol \" to allow the use of a quotation mark within a string.
So I've used a regex with capturing groups to grab each of the numbers and the N/S/E/W. After capturing each individually it's just a matter of doing a bit of dividing to get the numbers and then formatting them however you'd like. For example I went with 5 digits of precision here.
public static void main(String[] args) {
String coords = "78°14'09N 15°29'29E";
String[] decimalCoords = degreesToDecimal(coords);
System.out.println(decimalCoords[0]);
System.out.println(decimalCoords[1]);
}
public static String[] degreesToDecimal(String degMinSec) {
String[] result = new String[2];
Pattern p = Pattern.compile("(\\d+).*?(\\d+).*?(\\d+).*?([N|S|E|W]).*?(\\d+).*?(\\d+).*?(\\d+).*?([N|S|E|W]).*?");
Matcher m = p.matcher(degMinSec);
if (m.find()) {
int degLat = Integer.parseInt(m.group(1));
int minLat = Integer.parseInt(m.group(2));
int secLat = Integer.parseInt(m.group(3));
String dirLat = m.group(4);
int degLon = Integer.parseInt(m.group(5));
int minLon = Integer.parseInt(m.group(6));
int secLon = Integer.parseInt(m.group(7));
String dirLon = m.group(8);
DecimalFormat formatter = new DecimalFormat("#.#####", DecimalFormatSymbols.getInstance(Locale.ENGLISH));
formatter.setRoundingMode(RoundingMode.DOWN);
result[0] = formatter.format(degLat + minLat / 60.0 + secLat / 3600.0) + " " + dirLat;
result[1] = formatter.format(degLon + minLon / 60.0 + secLon / 3600.0) + " " + dirLon;
}
return result;
}
There is no error handling here, it's just a basic example of how you could make this work with your input.
I am trying to get a desired output based on a variable input. I can get close to what I want but there seems to be an issue with rounding a number.
What I want by example (input > output).
30 > 30
30.0 > 30
30.5 > 30,5
30.5555 > 30,6
30.04 > 30
The problem is that the last one comes back as 30.0. Now I understand why this is happening (because of the rounding up/down)
My code:
private String getDistanceString(double distance) {
distance = 30.55;
DecimalFormat df = new DecimalFormat(".#");
if (distance == Math.floor(distance)) {
//If value after the decimal point is 0 change the formatting
df = new DecimalFormat("#");
}
return (df.format(distance) + " km").replace(".", ",");
}
It is almost always wrong to use == with floating point numbers. You should use Math.abs(a - b) < x.
private String getDistanceString(double distance) {
DecimalFormat df = new DecimalFormat(".#");
if (Math.abs(distance - Math.round(distance)) < 0.1d) {
//If value after the decimal point is 0 change the formatting
df = new DecimalFormat("#");
}
return (df.format(distance) + " km").replace(".", ",");
}
public void test() {
double[] test = {30d, 30.0d, 30.5d, 30.5555d, 30.04d, 1d / 3d};
for (double d : test) {
System.out.println("getDistanceString(" + d + ") = " + getDistanceString(d));
}
}
A hack around it, is to replace with regex
return
(""+df.format(distance))
.replaceAll("\\.(0+$)?", ",") //replace . and trailing 0 with comma,
.replaceAll(",$","") //if comma is last char, delete it
+ " km"; //and km to the string
I'm getting a number from an addition of Int and then put it as String. I need to know what is the first, second etc. number of the addition. For example the number is 7654, how to know that "7" is the first number? And "6" the second? etc.
String result += "\nThe result of addition"
+ String.valueOf(add_1) + "+" + String.valueOf(add_2)
"+ is" + String.valueOf(int_result);
I want to know the number of a determinate position of the String that contain the result.
The string is String.valueOf(int_result), I can use directly int_result too.
Thanks!
Just walk each character in the resulting string:
String result = String.valueOf(int_result);
for (int i=0; i< result.length(); i++) {
char c = result.charAt(i);
System.out.println("Digit " + i + " = " + c);
// And if you need this as an integer
int digit = Integer.parseInt(""+c);
}
In Java to get the character at a particular position in a string just use this
String number ="7564";
char c = number.charAt(0);
The above code will asign '5' to char variable c. You can further parse it to integer by doing this
int i = Integer.parseInt(c);