String Functions

1. int length()  

As the name suggests, return the length of a string.  

Syntax: <int variable> = <String.length( )>;  

2. char charAt(int index) & int indexOf( char ch) 

charAt() function returns a character from the given index (position number) of the string.  Syntax: <char variable> = <String.charAt(int index)>;. indexOf() function is opposite to the charAt() function. It returns the index (i.e., the position number) of first occurrence of a character in the string. Syntax: <int variable> = <String.indexOf(character)>;    

3. int indexOf(char ch, int start_index) 

This function allows the user to search for the availability of a character in the string starting from the given index. Syntax: <int variable> = <String.indexOf(char ch, int start_index)>; 

4. int lastlndexOf(char ch) 

This function is used to find the index of the last occurrence of a character in the String.  

Syntax: <int variable>=<String lastlndexOf(character)>; 

5. String substring(int Start_index) & String substring(int start_index, int last_index) 

The substring(int start_index) function is used to extract a set of characters simultaneously from a given index up to the end of the string. substring(int start_index, int last_index) is another modification of substring function . It will return a set of characters simultaneously from start index upto the last index of the string (excluding the character present at the last index). 

6. String toLowerCase() & String toUpperCase() 

toLowerCase() function converts a given string into lowercase characters. Syntax: <String variable l > = <String.toLowerCase( )>; 

toUpperCase() function is opposite to the toLowerCase() function. It is used to convert a string into uppercase characters.  

7. String replace(char old_char, char new_char)  

This function is used to replace a character by another character or to replace a string by another string at all its occurrences in the given string. 

Syntax: <String variable 1> = <string.toUpperCase( )>; 

8. String replace(old sequence of characters, new sequence of characters) 

The replace() function is also used to replace a sequence of characters by another sequence of characters at all its occurences in the string. 

9. String concat(String s) 

The concat() function is used to concatenate Uoin) two strings together. Syntax: <String variable> = <string1.concat(string2)>;    

Here string 2 will be joined at the end of string 1. 

10. boolean equals(String s) & boolean equalslgnoreCase(String s) 

equals(string s) is used to compare two strings and check whether they are same or not. It treats uppercase and lowercase characters differently. equalsignoreCase(String s) does the same work but ignores the case. 

Syntax: <boolean variable> = <Stringl .equals(String2)>; 

11. int compareTo(String s) & int compareTolgnoreCase(String s) 

comapreTo(String s) It not only checks the equality of two strings but also checks whether a string is bigger or smaller than the other. It will return 0 if both the strings are same; a negative value, if first string is smaller and a positive value, if the first string is bigger. compareTolgnoreCase(String s) does the same work ignoring the upper and lower case. 

Syntax: <int variable> = <String 1.compareToignoreCase(String2)>; 

12. String trim() 

This function is used to remove leading and trailing blanks from a string. The other blanks, which are available in between the words will remain unchanged. 

Syntax: <String variable> = <String.trim( )>; 

13. boolean endsWith(String s) & boolean startsWith(String s) 

endsWith(String s)function is used to check whether a given string has a specified suffix or not. startsWith() returns boolean value true if the given string is a prefix to a given string.  

Syntax: <boolean variable>=<String 1.endswith(String2)>; 

14. primitive type valueOf(String s) 

Used to convert a string into primitive datatype.  

Syntax: <Primitive type> <Variable>= <Wrapper class>.<valueOf>(String argument); 

15. String valueOf(primitive type) 

Note: It is used to convert a primitive value into string. 

Syntax: String <variable> = String.valueOf(primitive type)