About overlapping strings(with. Java)

In this article, we learned about How to overlap strings (with. Java)

We’re going to learn by solving a coding test problem, reflecting on the problem we solved, and exploring other ways to solve it. Let’s start with the problem.

Problem

You are given the strings my_string, overwrite_string, and an integer s. Write a solution function that returns a string that replaces the string my_string with the string overwrite_string from index s in the string my_string to the length of overwrite_string.

Example input and output

my_string: He11oWor1d overwrite_string: lloWorl s: 2 result: HelloWorld

The problem is that the part of my_string from index 2 up to the length of overwrite_string is “11oWor1” and we need to return “HelloWorld” with this replaced by “lloWorl”.

My solution to the problem

class Solution {
    public String solution(String my_string, String overwrite_string, int s) {
        String answer = "";
        char[] a = my_string.toCharArray();
        char[] b = overwrite_string.toCharArray();
        int j = 0;
        int limit = s + b.length;
        for(int i = s; i<limit; i++){
            a[i] = b[j];
            j++;
        }
        answer = new String(a);
        return answer;
    }
}

In my case, I use the toCharArray() method to change two variables of string type, my_string and overwrite_string, to character array type. In this case, each character is mapped to one index. We then solved this problem by replacing the string from the sth element through j for each for statement. Finally, we combined the char array into a single String type using the new String() function and printed it out.

Now let’s look at a cleaner way of solving this problem using a function provided by java. This is substring(), which allows you to truncate a string type at any position.

How to use substring()

substring() takes two arguments: substring(int beginIndex, int endIndex) You can use it like this. With two arguments, this returns a string from beginIndex to endIndex.

substring(int beginIndex, int endIndex) Example

String str = "012345";

// substring(int beginIndex, int endIndex)
str.substring(1,3)

// result: 123

Alternatively, you can use only one argument, like this: substring(int previousIndex), which will return the rest of the string, starting from index 0 and ending with the number -1 of the int type written in previousIndex.

substring(int previousIndex) Example

String str = "012345";

// substring(int index)
str.substring(3)

// result: 345

Let’s try to solve the same problem using the substring() function we’ve learned so far, but more concisely than the code I wrote.

solved using substring()

class Solution {
    public String solution(String my_string, String overwrite_string, int s) {
        String before = my_string.substring(0, s);
        String after = my_string.substring(s + overwrite_string.length());
        return before + overwrite_string + after;
    }
}

That’s really short, and the code I wrote just truncated the string before and after to match the criteria in s and pasted the string to be changed. I’ll have to utilize this function in my next test problem, thanks for the work.