Boxing n Auto boxing-marcus green

[shilpa Reddy]

if anyone can pass on the link where boxing and auto boxing is explained clearly......if there are any tips on this by marcus green....it wuld be even more helpful....im having k&&b....i need some other link....also about regex classes and pattern matching....thanks in advance.....

[Marcus Green]

autoboxing

autoboxing addresses the code needed to get around the difference between primitives and the Wrapper classes used to store primitives. In the past it was necessary to call a method of the wrapper class to extract the primitive value. So the following code is typical.

           Integer i = new Integer(99);
                int j;
                j = i.intValue();
                System.out.println(j);

With Java 1.5 it is possible to write

public class AutoBox{
public static void main(String argv[]){
                AutoBox ab = new AutoBox();
                
        }
        AutoBox(){
                Integer i = new Integer(99);
                int j;
                j = i;
                System.out.println(j);
        }
}

Note how the instance of the integer class is assigned directly to the int primitive without any need for conversion. Note that if you are using mock exams from earlier versions of Java you may find that the behaviour of JDK1.5 means the answer is �incorrect�, but that it is simply because of the effect of autoboxing.

.

[shilpa Reddy]

thanks for your explanation.......i have another doubt in formatting

int i1 = -123;
int i2 = 12345;

System.out.printf(">%0,7d< \n", i2);
System.out.format(">%+-7d< \n", i2);

result is

>012,345<
>+12345 <

can you explain me this......how did the comma go between 012 and y the - symbol was not inserted....

thanks...

[Meena R. Krishnan]

--------------
System.out.printf(">%0,7d< \n", i2);
System.out.format(">%+-7d< \n", i2);
------------

7 represents the width of the output.
0 --> pad the o/p with zeros until it is of width 7
- --> left justifies the number and won't add - to the o/p
, --> is a grouping_separator.