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Revised: Tue Mar 29 11:14:56 CDT 2016
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This module discusses the String and StringBuffer classes in detail.
I recommend that you open another copy of this module in a separate browser window and use the following links to easily find and view the listings while you are reading about them.
A string in Java is an object. Java provides two different string classes from which objects that encapsulate string data can beinstantiated:
The String class is used for strings that are not allowed to change once an object has been instantiated (an immutable object) . The StringBuffer class is used for strings that may be modified by the program.
While the contents of a String object cannot be modified, a reference to a String object can be caused to point to a different String object as illustrated in the sample program shown in Listing 1 . Sometimes this makes it appear that the original String object is being modified.
| Listing 1 . File String01.java. |
|---|
/*File String01.java Copyright 1997, R.G.Baldwin
This application illustrates the fact that while a Stringobject cannot be modified, the reference variable can be
modified to point to a new String object which can havethe appearance of modifying the original String object.
The program was tested using JDK 1.1.3 under Win95.The output from this program is
Display original string valuesTHIS STRING IS NAMED str1
This string is named str2Replace str1 with another string
Display new string named str1THIS STRING IS NAMED str1 This string is named str2
Terminating program**********************************************************/
class String01{String str1 = "THIS STRING IS NAMED str1";
String str2 = "This string is named str2";public static void main(String[]args){
String01 thisObj = new String01();System.out.println("Display original string values");
System.out.println(thisObj.str1);System.out.println(thisObj.str2);
System.out.println("Replace str1 with another string");thisObj.str1 = thisObj.str1 + " " + thisObj.str2;
System.out.println("Display new string named str1");System.out.println(thisObj.str1);
System.out.println("Terminating program");}//end main()
}//end class String01 |
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