Searching Strings in Java

The String class provides two methods that allow you to search a string for a specified character or substring:

• indexOf( ) Searches for the first occurrence of a character or substring.
• lastIndexOf( ) Searches for the last occurrence of a character or substring

To search for the first occurrence of a character, use

          int indexOf(int ch)

To search for the last occurrence of a character, use

          int lastIndexOf(int ch)

Here, ch is the character being sought.

To search for the first or last occurrence of a substring, use

          int indexOf(String str)

          int lastIndexOf(String str)

Here, str specifies the substring.

You can specify a starting point for the search using these forms:

        int indexOf(int ch, int startIndex)
      int lastIndexOf(int ch, int startIndex)
      int indexOf(String str, int startIndex)
      int lastIndexOf(String str, int startIndex)

Here, startIndex specifies the index at which point the search begins. For indexOf( ), the search runs from startIndex to the end of the string. For lastIndexOf( ), the search runs from startIndex to zero.

// Demonstrate indexOf() and lastIndexOf().

class indexOfDemo {
public static void main(String args[]) {
String s = "Now is the time for all good men " +
"to come to the aid of their country.";
System.out.println(s);
System.out.println("indexOf(t) = " +
s.indexOf('t'));
System.out.println("lastIndexOf(t) = " +
s.lastIndexOf('t'));
System.out.println("indexOf(the) = " +
s.indexOf("the"));
System.out.println("lastIndexOf(the) = " +
s.lastIndexOf("the"));
System.out.println("indexOf(t, 10) = " +
s.indexOf('t', 10));
System.out.println("lastIndexOf(t, 60) = " +
s.lastIndexOf('t', 60));
System.out.println("indexOf(the, 10) = " +
s.indexOf("the", 10));
System.out.println("lastIndexOf(the, 60) = " +
s.lastIndexOf("the", 60));
}
} 

Output

Now is the time for all good men to come to the aid of their country.
indexOf(t) = 7
lastIndexOf(t) = 65
indexOf(the) = 7
lastIndexOf(the) = 55
indexOf(t, 10) = 11
lastIndexOf(t, 60) = 55
indexOf(the, 10) = 44
lastIndexOf(the, 60) = 55