substring() method

As the name of the method hints, substring() method of String class is used to extract a substring out of an invoked String object, starting at a particular index. There are two forms of substring() method, let's discuss each of those with example one by one.

Signature of the first form of substring() method

public String substring(int startIndex)

Access modifier - substring() method is a public method.
Parameter passed - An int index value, startIndex is passed to it.
Value returned - This method returns a substring String value which starts at startIndex and ends at the last index of the invoked String object. The returned substring should be stored or used, otherwise it is lost.

Note :

The startIndex int value is a zero-based index, hence the first index is counted as 0.

substring(int startIndex) example

Here in program below, we have a String object and we are extracting a substring out of it by calling the first form of substring() method i.e. substring(int startIndex) method.

// Program to find a substring of a String, starting at a specific index.


class StringSubstring
{
public static void main(String[] ar)
{
String str1= new String("0123456789");

String substring  = str1.substring(2);

System.out.println("Original String is "+ str1);
System.out.println("Substring from index 2 to the end :"+ substring );
}
}

Output is :


Original String is 0123456789
Substring from index 2 to the end :23456789

Program Analysis

In the coding example, we have initialized a string object with a value 0123456789.
Next we have called the substring() method to extract a substring starting at index position 2 and ending at the last index of invoked String object, hence, the extracted substring has a value 23456789.

Note: Because startIndex is an zero-based index int value, that's why the first index of a string is counted as 0.

Signature of the second form of substring() method

 public String substring(int startIndex, int endIndex)

Access modifier - substring() method is a public method.
Parameter passed - Two int index values, startIndex and endIndex are passed to it.
Value returned - This method returns a substring String value which starts at startIndex and ends at the endIndex. The returned substring should be stored or used, otherwise it is lost.

Note :

The startIndex int value is a zero-based index, hence the first index is counted as 0. In contrast, endIndex is an one-based index int value, hence, the first index in a string is counted as 1.

substring(int startIndex, int endIndex) example

Here in program below, we have a String object and we are extracting a substring out of it by calling the second form of substring() method i.e. substring(int startIndex, int endIndex) method.
```
// Program to find a substring of a String, starting and ending at specific indexes.


class StringSubstring
{
public static void main(String[] ar)
{
String str1= new String("0123456789");

String substring = str1.substring(2,5);

System.out.println("Original String is "+ str1);
System.out.println("Substring from index 2 to index 5 :"+ substring );
}
}
```
Output is :
```
Original String is 0123456789
Substring from index 2 to index 5 :234
```
Program Analysis
- In the coding example, we have initialized a string object with a value 0123456789.
- Next we have called the substring() method to extract a substring starting at index position 2 and ending at the index position 5 in the invoked string, hence, the extracted substring has a value 234.
Note: When calling the second form of substring() method, its endIndex argument is a one-based index int value i.e. the first index in a string is counted as 1, hence, the character at the endIndex(5), is 4.

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