Strings, Characters and Regular Expressions - Java: How to Program Early Objects - page 598

(a name) "John Q. Doe"

(a street address) "9999 Main Street"

(a city and state) "Waltham, Massachusetts"

(a telephone number) "[phone]"

A string may be assigned to a String reference. The declaration

String color = "blue" ;

initializes String variable color to refer to a String object that contains the string "blue" .

Performance Tip 14.1
To conserve memory, Java treats all string literals with the same contents as a single
String object that has many references to it.

14.3 Class String
Class String is used to represent strings in Java. The next several subsections cover many
of class String 's capabilities.

14.3.1 String Constructors
Class String provides constructors for initializing String objects in a variety of ways. Four
of the constructors are demonstrated in the main method of Fig. 14.1.

1 // Fig. 14.1: StringConstructors.java

2 // String class constructors.

3
4 public class StringConstructors

5 {

6 public static void main(String[] args)

7 {

8 char [] charArray = { 'b' , 'i' , 'r' , 't' , 'h' , ' ' , 'd' , 'a' , 'y' };

9 String s = new String( "hello" );

10
11 // use String constructors

String s1 = new String();
String s2 = new String(s);
String s3 = new String(charArray);
String s4 = new String(charArray, 6 , 3 );

12

13

14

15

16
17 System.out.printf(

18 "s1 = %s%ns2 = %s%ns3 = %s%ns4 = %s%n" , s1, s2, s3, s4);

19 }

20 } // end class StringConstructors

s1 =
s2 = hello
s3 = birth day
s4 = day

Fig. 14.1 | String class constructors.