USER-DEFINED METHODS - Java Programming: From Problem Analysis to Program Design - page 419

The assignment operator cannot be used with StringBuffer variables. You must use the
operator new to (initially) allocate memory space for a string.
The following example illustrates how objects of type StringBuffer are passed as parameters.

EXAMPLE 7-10

// This program illustrates how StringBuffer objects as
// parameters work.

public class StringBufferObjectsAsParameters //Line 1

{ //Line 2

public static void main(String[] args) //Line 3

{ //Line 4

StringBuffer str = new StringBuffer("Hello"); //Line 5

System.out.println("Line 6: str before "
+ "calling the method "
+ "stringBufferParameter: "
+ str); //Line 6

7

stringBufferParameter(str); //Line 7

System.out.println("Line 8: str after "
+ "calling the method "
+ "stringBufferParameter: "
+ str); //Line 8

} //end main //Line 9

public static void stringBufferParameter
(StringBuffer pStr)

//Line 10

{ //Line 11

System.out.println("Line 12: In the method "
+ "stringBufferParameter "); //Line 12

System.out.println("Line 13: pStr before "
+ "changing its value: "
+ pStr); //Line 13

pStr.append(" There"); //Line 14

System.out.println("Line 15: pStr after "
+ "changing its value: "
+ pStr); //Line 15

} //end stringBufferParameter //Line 16

} //Line 17

Sample Run:

Line 6: str before calling the method stringBufferParameter: Hello
Line 12: In the method stringBufferParameter
Line 13: pStr before changing its value: Hello
Line 15: pStr after changing its value: Hello There
Line 8: str after calling the method stringBufferParameter: Hello There