Strings are simply sequences of characters. In Java, strings are objects. The String class is used to create and manipulate strings. The easiest way to create a string is to write:
String helloString = "Hello world!";
“Hello world!” is a string literal, a sequence of characters enclosed in double quotes. Whenever the compiler encounters a string literal it creates a String object. You can also create a string literal using a keyword and a constructor. The String class has thirteen constructors. These allow you to specify the initial value of the string in different ways, for example:
char[] helloArray = { 'h', 'e', 'l', 'l', 'o', '.' }; String helloString = new String(helloArray); System.out.println(helloString);
The last line of this code fragment displays “hello” on the screen.
You can use the length() method, to determine the number of characters in a string object. The following code fragment would set the value of len to 26.
String palindrome = "Able was I, ere I saw Elba"; int len = palindrome.length();
You can use the concat() method to concatenate two strings (join them together):
string3 = string1.concat(string2);
String 3 will be string1 with string2 added to the end.
You can also use the concat() method with string literals:
"My name is ".concat("Dumbledore");
You can also concatenate strings using the + operator:
"Hello," + " world" + "!"
would produce the string “Hello, world!”
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