Strings

Many programs process text not numbers. Text consists of characters: letters, numbers, punctuation, spaces and so on. A String is a sequence of characters.

The String Type

You can declare variables that hold strings:

String name = "Harry";

name: String variable

"Harry" : string literal

The number of characters in a string is called the length of the string.

You can compute the length of a string with the length method.

int n = name.length();

A string of length 0 is called the empty string. It contains no characters and is written as "".

Concatenation

Use the + operator to concatenate strings, that is to put them together to yield a longer string.

String fName = "Harry";

String lName = "Potter";

String fullName = fName + " " + lName; // will return "Harry Potter"

When the expression to the left or the right of a + operator is a string, the other one is automatically forced to become a string as well, and both strings are concatenated.

String countryAndCode = "India" + " " + 91;

String Input

You can read string from console:

Use the next method of the Scanner class to read a string containing a single word.

String name = in.next();

Escape sequences

To include a quotation mark in a literal string, precede it with a backslash(\).

Ex: String quoteString = "He said, \"Hello\" ";

\n - new line character

\r - carriage return

Strings and Characters

Strings are a sequence of unicode characters. In Java, a character is a value of type char. Characters have numeric values.

'H' - character literal

"H" - string literal

The charAt method returns a char value from string. The first string position is labeled at 0, the second one 1, and so on.

String name = "Harry";

char start = name.charAt(0); // returns H

char last = name.charAt(4); // returns y

Substrings

Once you have a string, you can extract substrings by using the substring() method.

Syntax: str.substring(start, pastEnd);

returns a string that is made up of the characters in the string str, starting at position start, and containing all characters up to, but not including, the position pastEnd.

Ex:

String greeting = "Hello World!";

String sub = greeting.substring(0, 5); // returns Hello

If you omit the end position when calling the substring method, then all characters from the starting position to the end of the string are copied.

Note: The last character in string has position str.length() - 1