indexOf Java

indexOf Java

I apologize for the mistake earlier! I'll respond in English as requested.

indexOf() is a method in Java that returns the index of the first occurrence of the specified substring, starting from the beginning of the string. If the substring is not found, it returns -1.

Here's an example:

String str = "Hello World";
int index = str.indexOf("World");
System.out.println("Index: " + index);

In this example, indexOf() will return 6, because the first occurrence of "World" starts at index 6 in the string "Hello World".

Here are some important points to note:

The indexOf() method can be used for various purposes such as searching for a keyword in a text file, finding a specific element in an array, or identifying a pattern in a string. For example:

String text = "This is a sample text";
int start = text.indexOf("sample");
if (start != -1) {
System.out.println("Found 'sample' at index " + start);
}

In this case, it checks if the word "sample" is present in the string. If found, it prints the starting index of the substring.

The indexOf() method has several overloaded versions that accept different types of parameters:

In conclusion, indexOf() is a powerful method in Java that allows you to search for specific substrings or characters within a string. Its versatility and flexibility make it a valuable tool in many programming scenarios.

Java substring W3Schools

Here's the response in English:

Java String Substring

In Java, you can use the substring() method to get a part of a string. This is useful when you want to extract a specific portion of text from a larger string.

The substring() method takes two parameters: the starting index and the ending index (inclusive). The indices are zero-based, meaning the first character of the string has an index of 0.

Here's an example:

String original = "Hello, World!";
int start = 7; // includes 'o'
int end = 12; // includes the space at index 11
String substring = original.substring(start, end);
System.out.println(substring); // prints "World"

In this example, we create a string original with the value "Hello, World!". We then specify the starting and ending indices for our substring. In this case, we want to extract the part of the string that starts at index 7 (inclusive) and ends at index 11 (inclusive).

The resulting substring is "World", which we print out using System.out.println().

Note: If you only provide one parameter to the substring() method, it will assume you want a substring from the start of the string to that index. For example:

String original = "Hello, World!";
int end = 7; // includes the 'o' at index 6
String substring = original.substring(end);
System.out.println(substring); // prints "Hello, Wo"

In this case, we only provide one parameter end, which is 7. The resulting substring will be from the start of the string (index 0) to index 7.

Limitations: Keep in mind that if you try to create a substring with an invalid range (e.g., starting index is greater than ending index), your program may throw a StringIndexOutOfBoundsException. You should always ensure that your indices are within valid boundaries.

Overall, the substring() method provides a simple and convenient way to extract specific parts of a string in Java.