Strings, Characters and Regular Expressions - Java: How to Program Early Objects - page 617

concatenates "hello" , "BC" and 22 . The concatenation can be performed as follows:

String s = new StringBuilder().append( "hello" ).append( "BC" ).
append( 22 ).toString();

First, the preceding statement creates an empty StringBuilder , then appends to it the
strings "hello" and "BC" and the integer 22 . Next, StringBuilder 's toString method
converts the StringBuilder to a String object to be assigned to String s . The statement

s += "!" ;

can be performed as follows (this may differ by compiler):

s = new StringBuilder().append(s).append( "!" ).toString();

This creates an empty StringBuilder , then appends to it the current contents of s fol-
lowed by "!" . Next, StringBuilder 's method toString (which must be called explicitly
here) returns the StringBuilder 's contents as a String , and the result is assigned to s .

14.4.5 StringBuilder Insertion and Deletion Methods
StringBuilder provides overloaded insert methods to insert values of various types at
any position in a StringBuilder . Versions are provided for the primitive types and for
character arrays, String s, Object s and CharSequence s. Each method takes its second ar-
gument and inserts it at the index specified by the first argument. If the first argument is
less than 0 or greater than the StringBuilder 's length, a StringIndexOutOfBounds-
Exception occurs. Class StringBuilder also provides methods delete and deleteCharAt
to delete characters at any position in a StringBuilder . Method delete takes two argu-
ments—the starting index and the index one past the end of the characters to delete. All
characters beginning at the starting index up to but not including the ending index are de-
leted. Method deleteCharAt takes one argument—the index of the character to delete.
Invalid indices cause both methods to throw a StringIndexOutOfBoundsException .
Figure 14.14 demonstrates methods insert , delete and deleteCharAt .

1 // Fig. 14.14: StringBuilderInsertDelete.java

2 // StringBuilder methods insert, delete and deleteCharAt.

3
4 public class StringBuilderInsertDelete

5 {

6 public static void main(String[] args)

7 {

8 Object objectRef = "hello" ;

9 String string = "goodbye" ;

10 char [] charArray = { 'a' , 'b' , 'c' , 'd' , 'e' , 'f' };

11 boolean booleanValue = true ;

12 char characterValue = 'K' ;

13 int integerValue = 7 ;

14 long longValue = 10000000 ;

15 float floatValue = 2.5f ; // f suffix indicates that 2.5 is a float

16 double doubleValue = 33.333 ;

17

Fig. 14.14 | StringBuilder methods insert , delete and deleteCharAt . (Part 1 of 2.)