Java program to expand a String if range is given?

29 Sep, 2021
Suppose we have given a string in which some ranges as specified and we have to place the numbers which is between the given range in the specified place as provided and depicted in the illustration below as follows for a better understanding.
Illustration: 
Input  : string x = "1-5, 8, 11-14, 18, 20, 26-29" 
Output : string y = "1, 2, 3, 4, 5, 8, 11, 12, 
                    13, 14, 18, 20, 26, 27, 28, 29"
Approach: 
In order to solve the above problem, we can follow the below approach: 
First, we have to split the String into String[] array. We have to split the String where we found – symbol.
Now we have a String[] array with the elements. Now we just go to the first index last element i.e. 1 and the preceding index first element of the String[] array say it be 5.
After that with the help of for loop, we can add the numbers which are between 1 and 5 and store them in the String variable.
The above process continues till the length of the string array.
Note: 
With the help of Collections and various utility methods we can solve the problem easily but Collections concept is not a good option performance-wise. If we go through Collections, performance is reduced and time complexity is also increased.There in the below program we explicitly define our own split method and logic.
Implementation:
Here we will now be proposing and discussing all three scenarios with help of clean java program as follows:
Example 1
Java
// Java program to Expand a String if Range is Given // Main classpublic class Solution {     // Main driver method    public static void expand(String word)    {         // Creating an object of StringBuffer class to        // make a modifiable string object        StringBuilder sb = new StringBuilder();         // Get all intervals        String[] strArr = word.split(", ");         // Traverse through every interval        for (int i = 0; i < strArr.length; i++) {             // Get lower and upper            String[] a = strArr[i].split("-");             // Setting high and low counters            if (a.length == 2) {                 int low = Integer.parseInt(a[0]);                int high                    = Integer.parseInt(a[a.length - 1]);                 // Condition check holds true                // Till low counter is lesser or equal to                // high counter                while (low <= high) {                     // Append all numbers                    sb.append(low + " ");                    low++;                }            }             // If we reaches here then            // High counter exceeds lower counter            else {                 sb.append(strArr[i] + " ");            }        }         // Print the modifiable string        System.out.println(sb.toString());    }     // Method 2    // Main driver method    public static void main(String args[])    {        // Custom input string as input        String s = "1-5, 8, 11-14, 18, 20, 26-29";        expand(s);    }}
1 2 3 4 5 8 11 12 13 14 18 20 26 27 28 29
 
Example 2
Java
// Java Program to Illustrate Expansion of String // Main classpublic class StringExpand {     // Method 1    // To split the string    static String[] split(String st)    {        // Count how many words in our string        // Irrespective of spaces        int wc = countWords(st);        String w[] = new String[wc];        char[] c = st.toCharArray();        int k = 0;         for (int i = 0; i < c.length; i++) {             // Initially declaring and initializing            // string as empty            String s = "";             // Whenever we found an non-space character            while (i < c.length && c[i] != ' ') {                 // Concat with the String s                // Increment the value of i                s = s + c[i];                i++;            }             // If the String is not empty            if (s.length() != 0) {                 // Add the String to the String[]                // array                w[k] = s;                k++;            }        }         // Returning the string array        return w;    }     // Method 2    // To count the number of words in a string    static int countWords(String str)    {        int count = 0;        for (int i = 0; i < str.length(); i++) {             // The below condition to check            // whether the first character is            // space or not            if (i == 0 && str.charAt(i) != ' '                || str.charAt(i) != ' '                       && str.charAt(i - 1) == ' ') {                count++;            }        }         // Returning the count        return count;    }     // Method 3    // To expand the string    public static void expand(String s)    {        String p = s;        String[] arr = p.split("\\-");        String k = "";         // Traversing over array using for loop        for (int i = 0; i < arr.length; i++) {             // Case 1            if (i != arr.length - 1) {                 String[] arr1 = arr[i].split(", ");                String[] arr2 = arr[i + 1].split(", ");                 int a = Integer.parseInt(                    arr1[arr1.length - 1]);                int b = Integer.parseInt(arr2[0]);                 for (int j = a + 1; j < b; j++) {                    arr[i] = arr[i] + ", " + j;                }            }             // Case 2            if (k != "")                k = k + ", " + arr[i];             // Case 3            else                k = k + arr[i];        }         // Print the expanded string        System.out.println(k);    }     // Method 4    // Main driver method    public static void main(String[] args)    {        // Custom string input        String s = "1-5, 8, 11-14, 18, 20, 26-29";         // Calling the method 3 to        // expand the string        expand(s);    }}
1, 2, 3, 4, 5, 8, 11, 12, 13, 14, 18, 20, 26, 27, 28, 29
 
Example 3
Java
// Java program to Expand a String if Range is Given // Main class// GenerateStringOnRangeclass GFG {     // Method 1    // To generate string on range    public static String generateStringOn(String input)    {        String[] words = input.split(" ");         // Initially setting up range        String[] ranges = null;        int number = 0;         // Creating a StringBuffer object so that        // we can modify the string        StringBuffer buffer = new StringBuffer();         // Looking out for words by        // iterating using for each loop        for (String word : words) {                         // To be replaced by            // using replace() method            word = word.replace(",", "");             // If word is containing "-" character            if (word.contains("-")) {                ranges = word.split("-");                number = Integer.parseInt(ranges[0]);                 // Till number is within range                while (number                       <= Integer.parseInt(ranges[1])) {                                         // Append , in between them                    buffer.append(number + ", ");                    number++;                }            }             // If we reaches here then            // word does contains "-"            else {                buffer.append(word + ", ");            }        }         // Return the StringBuffer object        return buffer.toString();    }     // Method 2    // Main driver method    public static void main(String[] args)    {        // Custom input string        String input = "1-5, 8, 11-14, 18, 20, 26-29";         // Calling the method 1 as created above        System.out.println(generateStringOn(input));    }}
1, 2, 3, 4, 5, 8, 11, 12, 13, 14, 18, 20, 26, 27, 28, 29, 
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