Java Splitting With Math Expression

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I am trying to split a Math Expression.

String number = "100+500";

String[] split = new String[3];

I want to make

  • split[0] = "100"
  • split[1] = "+"
  • split[2] = "500"

I tried this but I don't know what to write for splitting.

split = number.split(????);

Split a math expression (Beginning Java forum at Coderanch), Java � Beginning Java. Split a math expression. Post by: Charlie Wall , Greenhorn. Feb 27, 2015 07:01:13. Hi guys. I have a small (well big to me) problem that I� To evaluate mathematical expression in String, use Nashorn JavaScript in Java i.e. scripting. Nashorn invoke dynamics feature, introduced in Java 7 to improve performance. For scripting, use the ScriptEngineManager class for the engine −

Off the bat, I don't know any library routine for the split. A custom splitting routine could be like this:

/**
 * Splits the given {@link String} at the operators +, -, * and /
 * 
 * @param string
 *            the {@link String} to be split.
 * @throws NullPointerException
 *             when the given {@link String} is null.
 * @return a {@link List} containing the split string and the operators.
 */
public List<String> split(String string) throws NullPointerException {
    if (string == null)
        throw new NullPointerException("the given string is null!");
    List<String> result = new ArrayList<String>();

    // operators to split upon
    String[] operators = new String[] { "+", "-", "*", "/" };

    int index = 0;
    while (index < string.length()) {
        // find the index of the nearest operator
        int minimum = string.length();
        for (String operator : operators) {
            int i = string.indexOf(operator, index);
            if (i > -1)
                minimum = Math.min(minimum, i);
        }

        // if an operator is found, split the string
        if (minimum < string.length()) {
            result.add(string.substring(index, minimum));
            result.add("" + string.charAt(minimum));
            index = minimum + 1;
        } else {
            result.add(string.substring(index));
            break;
        }
    }

    return result;
}

Some test code:

System.out.println(split("100+10*6+3"));
System.out.println(split("100+"));

Output:

[100, +, 10, *, 6, +, 3]
[100, +]

Evaluating an expression with integers, +, and *, as well as , java strings interview-questions math-expression-eval I would suggest using a smarter split expression, one that splits on the gaps for two things (the regex is in two parts - using "lookaround" expressions). (? approach, but there are many math parsers out there which you could check out for ideas. Java - String split() Method - This method has two variants and splits this string around matches of the given regular expression.

You can also use the Pattern/Matcher classes in Java:

    String expression = "100+34";
    Pattern p = Pattern.compile("(\\d+)|(\\+)");
    Matcher m = p.matcher(expression);
    String[] elems = new String[m.groupCount() +1];
    int i=0;

    while(m.find())
    {
        elems[i++] = m.group();
    }

Splitting or tokenising a string with Java regular expressions, String[] words = str.split("\\s+");. The regular expression that we pass to the String's split() method defines the pattern that we� Input String: 016-78967 Regular Expression: - Output : {"016", "78967"} Following are the two variants of split() method in Java: 1. Public String [ ] split ( String regex, int limit ) Parameters: regex - a delimiting regular expression Limit - the result threshold Returns: An array of strings computed by splitting the given string.

You can do something simple instead of insane regex; just pad + with white space:

String number = "100+500";
number = number.replace("+", " + ");

Now you can split it at the white space:

String[] split = number.split(" ");

Now your indices will be set:

split[0] = "100";
split[1] = "+";
split[2] = "500";

To check for all arithmetic symbols, you can use the following method if you wish to avoid regex:

public static String replacing(String s) {
   String[] chars = {"+", "-", "/", "="};

   for (String character : chars) {
      if (s.contains(character)) {
         s = s.replace(character, " " + character + " ");//not exactly elegant, but it works
      }
   }
   return s;
}

//in main method
number = replacing(number);
String[] split = number.split(" ");

Evaluating arithmetic expressions, An algorithm to evaluate arithmetic expressions. Here is an example Next, the program uses the String class's split method to split the input into an array of String objects. The middle The following Java class implements this data structure. Java String split method is used for splitting a String into its substrings based on the given delimiter or regular expression.. For example: String: [email protected] Regular Expression: @ Output : {"chaitanya", "singh"}

You can split your expression string, then in result having pure tokens and categorized tokens. The mXparser library supports this as well as the calculation process. Please follow the below example:

Your very simple example "100+500":

import org.mariuszgromada.math.mxparser.*;
...
...
Expression e = new Expression("100+500");
mXparser.consolePrintTokens( e.getCopyOfInitialTokens() );

Result:

[mXparser-v.4.0.0]  --------------------
[mXparser-v.4.0.0] | Expression tokens: |
[mXparser-v.4.0.0]  ---------------------------------------------------------------------------------------------------------------
[mXparser-v.4.0.0] |    TokenIdx |       Token |        KeyW |     TokenId | TokenTypeId |  TokenLevel |  TokenValue |   LooksLike |
[mXparser-v.4.0.0]  ---------------------------------------------------------------------------------------------------------------
[mXparser-v.4.0.0] |           0 |         100 |       _num_ |           1 |           0 |           0 |       100.0 |             |
[mXparser-v.4.0.0] |           1 |           + |           + |           1 |           1 |           0 |         NaN |             |
[mXparser-v.4.0.0] |           2 |         500 |       _num_ |           1 |           0 |           0 |       500.0 |             |
[mXparser-v.4.0.0]  ---------------------------------------------------------------------------------------------------------------

More sophisticated example "2*sin(x)+(3/cos(y)-e^(sin(x)+y))+10":

import org.mariuszgromada.math.mxparser.*;
...
...
Argument x = new Argument("x");
Argument y = new Argument("y");
Expression e = new Expression("2*sin(x)+(3/cos(y)-e^(sin(x)+y))+10", x, y);
mXparser.consolePrintTokens( e.getCopyOfInitialTokens() );

Result:

[mXparser-v.4.0.0]  --------------------
[mXparser-v.4.0.0] | Expression tokens: |
[mXparser-v.4.0.0]  ---------------------------------------------------------------------------------------------------------------
[mXparser-v.4.0.0] |    TokenIdx |       Token |        KeyW |     TokenId | TokenTypeId |  TokenLevel |  TokenValue |   LooksLike |
[mXparser-v.4.0.0]  ---------------------------------------------------------------------------------------------------------------
[mXparser-v.4.0.0] |           0 |           2 |       _num_ |           1 |           0 |           0 |         2.0 |             |
[mXparser-v.4.0.0] |           1 |           * |           * |           3 |           1 |           0 |         NaN |             |
[mXparser-v.4.0.0] |           2 |         sin |         sin |           1 |           4 |           1 |         NaN |             |
[mXparser-v.4.0.0] |           3 |           ( |           ( |           1 |          20 |           2 |         NaN |             |
[mXparser-v.4.0.0] |           4 |           x |           x |           0 |         101 |           2 |         NaN |             |
[mXparser-v.4.0.0] |           5 |           ) |           ) |           2 |          20 |           2 |         NaN |             |
[mXparser-v.4.0.0] |           6 |           + |           + |           1 |           1 |           0 |         NaN |             |
[mXparser-v.4.0.0] |           7 |           ( |           ( |           1 |          20 |           1 |         NaN |             |
[mXparser-v.4.0.0] |           8 |           3 |       _num_ |           1 |           0 |           1 |         3.0 |             |
[mXparser-v.4.0.0] |           9 |           / |           / |           4 |           1 |           1 |         NaN |             |
[mXparser-v.4.0.0] |          10 |         cos |         cos |           2 |           4 |           2 |         NaN |             |
[mXparser-v.4.0.0] |          11 |           ( |           ( |           1 |          20 |           3 |         NaN |             |
[mXparser-v.4.0.0] |          12 |           y |           y |           1 |         101 |           3 |         NaN |             |
[mXparser-v.4.0.0] |          13 |           ) |           ) |           2 |          20 |           3 |         NaN |             |
[mXparser-v.4.0.0] |          14 |           - |           - |           2 |           1 |           1 |         NaN |             |
[mXparser-v.4.0.0] |          15 |           e |           e |           2 |           9 |           1 |         NaN |             |
[mXparser-v.4.0.0] |          16 |           ^ |           ^ |           5 |           1 |           1 |         NaN |             |
[mXparser-v.4.0.0] |          17 |           ( |           ( |           1 |          20 |           2 |         NaN |             |
[mXparser-v.4.0.0] |          18 |         sin |         sin |           1 |           4 |           3 |         NaN |             |
[mXparser-v.4.0.0] |          19 |           ( |           ( |           1 |          20 |           4 |         NaN |             |
[mXparser-v.4.0.0] |          20 |           x |           x |           0 |         101 |           4 |         NaN |             |
[mXparser-v.4.0.0] |          21 |           ) |           ) |           2 |          20 |           4 |         NaN |             |
[mXparser-v.4.0.0] |          22 |           + |           + |           1 |           1 |           2 |         NaN |             |
[mXparser-v.4.0.0] |          23 |           y |           y |           1 |         101 |           2 |         NaN |             |
[mXparser-v.4.0.0] |          24 |           ) |           ) |           2 |          20 |           2 |         NaN |             |
[mXparser-v.4.0.0] |          25 |           ) |           ) |           2 |          20 |           1 |         NaN |             |
[mXparser-v.4.0.0] |          26 |           + |           + |           1 |           1 |           0 |         NaN |             |
[mXparser-v.4.0.0] |          27 |          10 |       _num_ |           1 |           0 |           0 |        10.0 |             |
[mXparser-v.4.0.0]  ---------------------------------------------------------------------------------------------------------------

To understand what Token.tokenId and Token.tokenTypeId means you need to refer to the API documentation and parsertokens section. For instance in Operator class you have

  1. Operator.TYPE_ID - this corresponds to Token.tokenTypeId if Token is recognized as Operator
  2. Operator.OPERATOR_NAME_ID - this corresponds to Token.tokenId if Token is recognized as particular OPERATOR_NAME.

Please follow mXparser tutorial for better understanding.

Best regards

Parsing Strings with split, Strings in Java can be parsed using the split method of the String class. Suppose we are representing arithmetic expressions using strings and wish to parse� The Java Math class provides more advanced mathematical calculations than what the basic Java math operators provide. The Math class contains methods for finding the maximum or minimum of two values, rounding values, logarithmic functions, square root, and trigonometric functions (sin, cos, tan etc.).

Split strings at delimiters - MATLAB split, newStr = split( str ) divides str at whitespace characters and returns the result as the output array newStr . The input array str can be a string array, a character� regex − This is the delimiting regular expression. Return Value. This method returns the array of strings computed by splitting this string around matches of the given regular expression. Exception. PatternSyntaxException − if the regular expression's syntax is invalid. Example. The following example shows the usage of java.lang.String

How to evaluate a math expression given in string form?, Evaluating a math expression given in string form, I'm trying to write a Java the String class's split() method to split the input String into an array of Strings. I have a math expression in a String, that I want to split into 4 pieces as in the following example: String math = "23+4=27" int num1 = (23 STORES HERE) int num2 = (4 STORES HERE) String operator = (+ STORES HERE) int answer = (27 STORES HERE) Note that the operator can be either + - * / I appreciate your help

Java Expressions Library, The main design goal was to create light weight expression compiler Support for all Java arithmetic operators: + (add),- (subtract), * (multiply), / (divide),� The array contains substrings of the specified string after splitting. For example, you may require breaking the phone numbers that are in that format: 123-345-7898. Similarly, strings to break where comma occurs etc. Full string split example with limit parameter example Syntax of split Java method. Following are the ways of using the split

Comments
  • Why do you want to split it? To write a parser or to evaluate the expression? In both cases split is probably not the right tool.
  • @assylias I am making a GUI Calculator for Big Integers. After splitting, I will check which operator used, then I will evaluate it.
  • Split uses regex, so this may be interesting: stackoverflow.com/questions/24463048/…
  • Ah shoot, I misread this question. Split probably is not the best tool for the job, as it will consume the character it's splitting on.
  • @Makoto yeah I tried it but I couldn't get the operator. I will just use +,- and * operators so all I have to do is split these 3.
  • It worked... but how? What does "(?<=\\d)(?=\\D)|(?<=\\D)(?=\\d)" mean?
  • @Dosher: Check out docs.oracle.com/javase/tutorial/essential/regex. Predefined Character classes will explain what the \d and \D do. The other methods should explain the rest of the regex.
  • @Bohemian That helped me a lot, now I understand it. Thank you so much!
  • Updated to return an array as in the example.
  • That is a great method for me but I also need to split - and . Will number = number.replace("+", " + " || "-", " - " || "", " * "); work? --Edit : OK it didn't work.
  • Unfortunately, you would have to include a .replace() for every character you wish to pad for this technique to work. A workaround is to create a method that will check for all areas desired to split, and constantly update the String, then return it. Your characters, such as * and - can be placed in an array to be iterated through. The benefit is you only have to write replace() once, so your code will look more elegant. Performance would still be the same though.