Substring.A string has 10 characters, but we want only a part of this string—the first 5, the last 3. With substring we get a string from within an existing string.
First example.Let us begin with this example. We have an input string "cat123." To get the "cat" part, we use a first index of 0, and a last index of 3.Strings
First argument: The index of the first char we are taking a substring at—the first char in a string is at index 0.
Second argument: The last index of the substring. This is not a count, but rather another position in the string.
Substring, 1 argument.Substring can be used with just 1 argument. This is the start index. We can think of this argument as the number of characters we want to skip over.
Length: For substring with 1 argument, the remaining part of the string (after the index specified) is included.
Performance, reuse substring.Should we try to reuse substrings? In this benchmark we test whether reusing a single substring in a loop is faster than computing a substring each time.
Version 1: This script gets a substring on each iteration of the loop. So many substrings are created.
Version 2: This version computes a substring once, and then reuses it on each iteration of the loop. One substring is created only.
Result: Creating and reusing one substring is the faster approach. So reducing substring calls helps performance.
CharAt, char indexes.For accessing an individual character in a string, consider charAt or directly accessing a character. For performance, directly using a character is a good solution.charAt
With substring,we have a way to extract parts of strings. For optimal performance, using the original string and not changing it at all is best, but this is not always possible.
Dot Net Perls
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