class toStringDemo {
public static void main(String args[]) {
Box b = new Box(10, 12, 14);
String s = "Box b: " + b; // concatenate Box object
System.out.println(b); // convert Box to string
System.out.println(s);
}
}
The output of this program is shown here:
Dimensions are 10.0 by 14.0 by 12.0
Box b: Dimensions are 10.0 by 14.0 by 12.0
As you can see, Box's toString( ) method is automatically invoked when a Box object
is used in a concatenation expression or in a call to println( ).
Character Extraction
The String class provides a number of ways in which characters can be extracted from a
String object. Each is examined here. Although the characters that comprise a string within
a String object cannot be indexed as if they were a character array, many of the String methods
employ an index (or offset) into the string for their operation. Like arrays, the string indexes
begin at zero.
charAt( )
To extract a single character from a String, you can refer directly to an individual character
via the charAt( ) method. It has this general form:
char charAt(int where)
Here, where is the index of the character that you want to obtain. The value of where must be
nonnegative and specify a location within the string. charAt( ) returns the character at the
specified location. For example,
char ch;
ch = "abc".charAt(1);
assigns the value "b" to ch.
getChars( )
If you need to extract more than one character at a time, you can use the getChars( ) method.
It has this general form:
void getChars(int sourceStart, int sourceEnd, char target[ ], int targetStart)
Here, sourceStart specifies the index of the beginning of the substring, and sourceEnd
specifies an index that is one past the end of the desired substring. Thus, the substring contains
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