Thanks for checking out my question.
Starting off, the program has the following goal; the user inputs currency formatted as "xD xC xP xH"; the program checks the input is correct and then prints back the 'long' version: "x Dollars, x Cents, x Penny's, x half penny's"
Here I have some code that takes input from user as String currencyIn, splits the string into array tokens, then replaces the D's with Dollars etc and prints the output.
public class parseArray
{
public parseArray()
{
System.out.print('\u000c');
String CurrencyFormat = "xD xS xP xH";
System.out.println("Please enter currency in the following format: \""+CurrencyFormat+"\" where x is any integer");
System.out.println("\nPlease take care to use the correct spacing enter the exact integer plus type of coin\n\n");
Scanner input = new Scanner(System.in);
String currencyIn = input.nextLine();
currencyIn.toUpperCase();
System.out.println("This is the currency you entered: "+currencyIn);
String[] tokens = currencyIn.split(" ");
for (String t : tokens)
{
System.out.println(t);
}
String dollars = tokens[0].replaceAll("D", " Dollars ");
String cents = tokens[1].replaceAll("C", " cents");
String penny = tokens[2].replaceAll("P", " Penny's");
String hPenny = tokens[3].replaceAll("H", " Half penny's");
System.out.println(" "+dollars+ " " +cents+ " " +penny+ " " +hPenny);
input.close();
}
}
Question 1: At the moment the program prints out pretty anything you put in. how do I establish some input control? I've seen this done in textbooks with switch statement and a series of if statements, but were too complicated for me. Would it parse characters using charAt() for each element of the array?
Question 2: Is there a 'better' way to print the output? My friend said converting my 4 strings (dollars, cents, penny's, hpenny's) into elements 0, 1, 2, 3 of a new array (called newArray) and print like this:
System.out.println(Arrays.toString(newArray));
Many thanks in advance.
There is a neat solution, involving Regular Expressions, Streams and some lambdas. Core concept is that we define the input format through a regular expression. We need some sequence of digits, followed by a 'D' or a 'd', followed by a " ", followed by a sequence of digits, followed by a C or c,... I will skip derivation of this pattern, it is explained in the regular expression tutorial I linked above. We will find that
final String regex = "([0-9]+)[D|d]\\ ([0-9]+)[C|c]\\ ([0-9]+)[P|p]\\ ([0-9]+)[H|h]";
satisfies our needs. With this regular expression we can now determine whether our input String has the right format (input.matches(regex)), as well as extract the bits of information we are actually interested in (input.replaceAll(regex, "$1 $2 $3 $4"). Sadly, replaceAll yields another String, but it will contain the four digit sequences we are interested in, divided by a " ". We will use some stream-magic to transform this String into a long[] (where the first cell holds the D-value, the second holds the C-value,...). The final program looks like this:
import java.util.Arrays;
public class Test {
public static void main(String... args) {
final String input = args[0];
final String regex =
"([0-9]+)[D|d]\\ ([0-9]+)[C|c]\\ ([0-9]+)[P|p]\\ ([0-9]+)[H|h]";
if (input.matches(regex) == false) {
throw new IllegalArgumentException("Input is malformed.");
}
long[] values = Arrays.stream(input.replaceAll(regex, "$1 $2 $3 $4").split(" "))
.mapToLong(Long::parseLong)
.toArray();
System.out.println(Arrays.toString(values));
}
}
If you want to have a List<Long> instead a long[] (or a List<Integer> instead of an int[]), you would use
List<Long> values = Arrays.stream(input.replaceAll(regex, "$1 $2 $3 $4").split(" "))
.map(Long::parseLong)
.collect(Collectors.toList());
It is necessary to change mapToLong to map to receive a Stream<Long> instead of a LongStream. I am sure that one could somehow write a custom Collector for LongStream to transform it into a List<Long>, but I found this solution more readable and reliable (after all, the Collector used comes from Oracle, I trust they test their code extensively).
Here is some example call:
$> java Test "10D 9c 8p 7H"
[10, 9, 8, 7]
$> java Test "10E 9C 8P 7H"
Exception in thread "main" java.lang.IllegalArgumentException: Input is malformed.
at Test.main(Test.java:10)
$> java Test "10D 9C 8P 7H 10D 9C 8P 7H"
Exception in thread "main" java.lang.IllegalArgumentException: Input is malformed.
at Test.main(Test.java:10)
Question1
You can actually check if the input is what it's supposed to be with simple checks. For example, you can check the first element like this:
if(tokens[0].charAt(1).equals("D"))
return true;
else
return false;
Another way to check if the input is correct is by using Regular Expressions, but I assume you are a beginner and this is too much trouble for you, although it is the better way. So I leave it to you to look through it later.
Question2
You can actually listen to your friend and do as they said. You can write it as follows:
for(int i = 0; i < 4; i++)
System.out.print(" " + tokens[i])
System.out.println();
Or you may use
System.out.println(Arrays.toString(newArray));
And you have saved newArray like this:
newArray[0] = " " + tokens[0];
you could use the .equals() method to see if what a user has typed in matches what you have
if (currencyIn.equals("CurrencyFormat"))
{
...
}
this is probably the simplest way i can think of!
Related
This is for AOC day 2. The input is something along the lines of
"6-7 z: dqzzzjbzz
13-16 j: jjjvjmjjkjjjjjjj
5-6 m: mmbmmlvmbmmgmmf
2-4 k: pkkl
16-17 k: kkkkkkkkkkkkkkkqf
10-16 s: mqpscpsszscsssrs
..."
It's formatted like 'min-max letter: password' and seperated by line. I'm supposed to find how many passwords meet the minimum and maximum requirements. I put all that prompt into a string variable and used Pattern.quote("\n") to seperate the lines into a string array. This worked fine. Then, I replaced all the letters except for the numbers and '-' by making a pattern Pattern.compile("[^0-9]|-"); and running that for every index in the array and using .trim() to cut off the whitespace at the end and start of each string. This is all working fine, I'm getting the desired output like 6 7 and 13 16.
However, now I want to try and split this string into two. This is my code:
HashMap<Integer,Integer> numbers = new HashMap<Integer,Integer>();
for(int i = 0; i < inputArray.length; i++){
String [] xArray = x[i].split(Pattern.quote(" "));
int z = Integer.valueOf(xArray[0]);
int y = Integer.valueOf(xArray[1]);
System.out.println(z);
System.out.println(y);
numbers.put(z, y);
}
System.out.println(numbers);
So, first making a hasmap which will store <min, max> values. Then, the for loop (which runs 1000 times) splits every index of the 6 7 and 13 16 string into two, determined by the " ". The System.out.println(z); and System.out.println(y); are working as intended.
6
7
13
16
...
This output goes on to give me 2000 integers seperated by a line each time. That's exactly what I want. However, the System.out.println(numbers); is outputting:
{1=3, 2=10, 3=4, 4=7, 5=6, 6=9, 7=12, 8=11, 9=10, 10=18, 11=16, 12=13, 13=18, 14=16, 15=18, 16=18, 17=18, 18=19, 19=20}
I have no idea where to even start with debugging this. I made a test file with an array that is formatted like "even, odd" integers all the way up to 100. Using this exact same code (I did change the variable names), I'm getting a better output. It's not exactly desired since it starts at 350=351 and then goes to like 11=15 and continues in a non-chronological order but at least it contains all the 100 keys and values.
Also, completely unrelated question but is my formatting of the for loop fine? The extra space at the beginning and the end of the code?
Edit: I want my expected output to be something like {6=7, 13=16, 5=6, 2=4, 16=17...}. Basically, the hashmap would have the minimum and maximum as the key and value and it'd be in chronological order.
The problem with your code is that you're trying to put in a nail with a saw. A hashmap is not the right tool to achieve what you want, since
Keys are unique. If you try to input the same key multiple times, the first input will be overwritten
The order of items in a HashMap is undefined.
A hashmap expresses a key-value-relationship, which does not exist in this context
A better datastructure to save your Passwords would probably just be a ArrayList<IntegerPair> where you would have to define IntegerPair yourself, since java doesn't have the notion of a type combining two other types.
I think you are complicating the task unnecessarily. I would proceed as follows:
split the input using the line separator
for each line remove : and split using the spaces to get an array with length 3
build from the array in step two
3.1. the min/max char count from array[0]
3.2 charachter classes for the letter and its negation
3.3 remove from the password all letters that do not correspond to the given one and check if the length of the password is in range.
Something like:
public static void main(String[] args){
String input = "6-7 z: dqzzzjbzz\n" +
"13-16 j: jjjvjmjjkjjjjjjj\n" +
"5-6 m: mmbmmlvmbmmgmmf\n" +
"2-4 k: pkkl\n" +
"16-17 k: kkkkkkkkkkkkkkkqf\n" +
"10-16 s: mqpscpsszscsssrs\n";
int count = 0;
for(String line : input.split("\n")){
String[] temp = line.replace(":", "").split(" "); //[6-7, z, dqzzzjbzz]
String minMax = "{" + (temp[0].replace('-', ',')) + "}"; //{6,7}
String letter = "[" + temp[1] + "]"; //[z]
String letterNegate = "[^" + temp[1] + "]"; //[^z]
if(temp[2].replaceAll(letterNegate, "").matches(letter + minMax)){
count++;
}
}
System.out.println(count + "passwords are valid");
}
I've found the following with unexpected results:
format number result expected
"000-00-0000" 123456789L "123456789--" "123-45-6789"
"(###)###-####" 1234567890L "(1234567890)-" "(123)456-7890"
"_($* "-"_)" 0 " $ \t- 0" " $ \t- "
Can it not handle non-number formats like phone numbers, social security numbers, etc?
It could probably be hacked to do so, but it's has not been created for this purposes.
These kind of tasks could be taken up by regular expressions and be far more effective and expressive.
The first example could be simplified to the following
String regex = "^(\\d{3})(\\d{2})(\\d{4})$";
String input = 123456789L + "";
System.out.println(input.replaceAll(regex, "$1-$2-$3")); // 123-45-6789
The second one to the following
String regex = "^(\\d{3})(\\d{3})(\\d{4})$";
String input = 1234567890L + "";
System.out.println(input.replaceAll(regex, "($1)$2-$3")); // (123)456-7890
And so on...
import java.util.Scanner;
public class CashSplitter {
public static void main(String[] args) {
Scanner S = new Scanner(System.in);
System.out.println("Cash Values");
String i = S.nextLine();
for(int b = 0;b<i.length(); b ++){
System.out.println(b);
System.out.println(i.substring(0,i.indexOf('.')+3));
i.replace(i.substring(0, i.indexOf('.') + 3), "");
System.out.println(i);
System.out.println(i.substring(0, i.indexOf('.') + 3));
}
}
}
The code should be able to take a string with multiple cash values and split them up, into individual values. For example 7.32869.32 should split out 7.32, 869.32 etc
A string is immutable, therefore replace returns a new String for you to use
try
i = i.replace(i.substring(0, i.indexOf('.') + 3), "");
Although try using
https://docs.oracle.com/javase/7/docs/api/java/text/NumberFormat.html
There are several problems with your code:
You want to add two, not three, to the index of the decimal point,
You cannot use replace without assigning back to the string,
Your code assumes that there are no identical cash values.
For the last point, if you start with 2.222.222.22, you would get only one cash value instead of three, because replace would drop all three matches.
Java offers a nice way of splitting a String on a regex:
String[] parts = S.split("(?<=[.]..)")
Demo.
The regex is a look-behind that expects a dot followed by any two characters.
Questions like this one have been answered but none helped me understand and decide the best suited way to do this in my case.
The idea:
Input: 15k+5b-1m
Ouput: 15000+5000000000-1000000
Basically replacing k by 1,000 - m by 1,000,000 and b by 1,000,000,000 and multiply it to the value it is attached to.
How I thought I'd do it:
Using 2 StringTokenizer, one to parse math signs +,-,*,/ and one to parse
letter k,m,b that I call on every element the first parser got.
So if we apply the algorithm we'd have for my example:
Str Input = 15k+5b-1m
StringTokenizer math_token= new StringTokenizer(source, Input);
while (math_token.hasMoreTokens())
{
while(math_token.hasMoreElements())
{
Str token_value = math_token.nextElement();
parse_letters(token_value) and change values...
}
math_token.nextToken();
format stuff for the final string
}
So it goes like:
15k -> 15 -> 15000
If I understand your question, then you could replace b with nine zeros m with six zeros and k with three zeros. Also, by convention, Java variable names start with a lower-case letter. Something like,
String input = "15k+5b-1m";
input = input.replace("b", "000000000").replace("m", "000000")
.replace("k", "000");
System.out.println(input);
which outputs (as requested)
15000+5000000000-1000000
The user enters an array of numbers such as "123456789"
and then the user is supposed to enter a string of commands such as "PE"
and my program will check each character in the string.
P = Remove the last number entered, which is 9
E = Prints out the final result.
To this point everything was working fine.
But my problem is that I have to be able to read the command when the user inputs "P(any number)", and I have to place that number at the end of the array of numbers.
So if it was P(4), the result would be "1234567894".
How can I do this ?
This is what I have right now for P and E.
if (commandList.get(x).equals("P(")) {
JOptionPane.showMessageDialog(null, "HI");
}
else if (commandList.get(x).equals("P")) {
strList.remove(strList.size()-1);
x++;
}
As far as I understand, your problem is to extract the 'digit' from the string "P(digit)" ?
Well you have to parse the input string, e.g., by searching for bounding characters, here '(' and ')'. For example by something like that:
String s = "P(3)";
String number = s.substring(s.indexOf("(") + 1, s.indexOf(")"));
strList.append(number);
But this would also accept anything within the bracktes, e.g., "foooo" from "P(foooo)", and it would crash if ')' cannot be found, e.g., s = "P(123", and it would accept "P(3)blah54" which is strictly spoken invalid. To improve your parser, you can use regular expressions, e.g., to check if the input is exactly of the form "P(2)" for exactly a single digit, you can use
String s = "P(3)";
if (!s.matches("P\\(\\d\\)"))
throw new RuntimeException("invalid input format: " + s);
String number = s.substring(s.indexOf("(") + 1, s.indexOf(")"));
strList.append(number);
If you explicitly want to cast the digit to an int, you might have a look at Integer.parseInt(...), e.g.,
int i = Integer.parseInt(number);