Strings, Characters and Regular Expressions - Java: How to Program Early Objects - page 611

25 System.out.printf( "int = %s%n" , String.valueOf(integerValue)

String.valueOf(longValue)
String.valueOf(floatValue)

);

26 System.out.printf( "long = %s%n" , );

27 System.out.printf( "float = %s%n" , );

28

System.out.printf(

29

String.valueOf(doubleValue)
String.valueOf(objectRef)

"double = %s%n" , );

30

System.out.printf( "Object = %s" , );

31

}

32

} // end class StringValueOf

char array = abcdef
part of char array = def
boolean = true
char = Z
int = 7
long = 10000000000
float = 2.5
double = 33.333
Object = hello

Fig. 14.9 | String valueOf methods. (Part 2 of 2.)

There are seven other versions of method valueOf , which take arguments of type
boolean , char , int , long , float , double and Object , respectively. These are demon-
strated in lines 21-30. The version of valueOf that takes an Object as an argument can
do so because all Object s can be converted to String s with method toString .
[ Note: Lines 12-13 use literal values 10000000000L and 2.5f as the initial values of
long variable longValue and float variable floatValue , respectively. By default, Java
treats integer literals as type int and floating-point literals as type double . Appending the
letter L to the literal 10000000000 and appending letter f to the literal 2.5 indicates to the
compiler that 10000000000 should be treated as a long and 2.5 as a float . An uppercase
L or lowercase l can be used to denote a variable of type long and an uppercase F or low-
ercase f can be used to denote a variable of type float .]

14.4 Class StringBuilder
We now discuss the features of class StringBuilder for creating and manipulating dynam-
ic string information—that is, modifiable strings. Every StringBuilder is capable of stor-
ing a number of characters specified by its capacity . If a StringBuilder 's capacity is
exceeded, the capacity expands to accommodate the additional characters.

Performance Tip 14.3
Java can perform certain optimizations involving String objects (such as referring to one
String object from multiple variables) because it knows these objects will not change.
String s (not StringBuilder s) should be used if the data will not change.

Performance Tip 14.4
In programs that frequently perform string concatenation, or other string modifications,
it's often more efficient to implement the modifications with class StringBuilder .