String substring()

The substring() method is a part of the String class and is used to extract a portion of a string. It returns a new string that represents the specified substring.

The basic syntax of the substring() method is as follows:

String substring(int beginIndex)
String substring(int beginIndex, int endIndex)

Here’s how you can use it:

1. Using a single argument (beginIndex):

String original = "Hello, world!";
String substring = original.substring(7); // "world!"

In this example, calling substring(7) extracts the portion of the original string starting from index 7 (inclusive) to the end of the string.

2. Using two arguments (beginIndex and endIndex):

String original = "Hello, world!";
String substring = original.substring(0, 5); // "Hello"

In this example, calling substring(0, 5) extracts the portion of the original string starting from index 0 (inclusive) up to index 5 (exclusive), which results in the substring “Hello”.

It’s important to note the following about the substring() method:

• The beginIndex is inclusive, meaning the character at that index is included in the substring.
• The endIndex is exclusive, meaning the character at that index is not included in the substring.
• If you provide only one argument (beginIndex), the substring will be extracted from that index to the end of the string.
• If you provide two arguments (beginIndex and endIndex), the substring will be extracted from beginIndex up to, but not including, endIndex.
• If the beginIndex is greater than or equal to the length of the string, an empty string is returned.
• If the endIndex is greater than the length of the string, it is automatically adjusted to the length of the string.

Here are a few more examples:

String original = "abcdef";
String sub1 = original.substring(2, 4); // "cd"
String sub2 = original.substring(1, 3); // "bc"
String sub3 = original.substring(4);    // "ef"

Keep in mind that the substring() method returns a new string that represents the extracted substring. The original string remains unchanged.