how to subtract two strings

[preethi Ayyappan]

Hi,

I am having a string variable,say

String a="30"

and another string variable

String b="1"

.

Now i need to subtract 1 from 30.How do i subtract these two things.
please assist me to do this.

Thanks

[Seetharaman Venkatasamy]

Convert String to int [premitive]

[Harshit Rastogi]

you can use

 Integer.valueOf(String s) 

to parse the value..

[Seetharaman Venkatasamy]

 

Harshit Rastogi wrote:you can use

 Integer.valueOf(String s) 

to parse the value..

return type of the valueOf is wrapper(Integer) . this wont be much flexible in terms of mathematical operations .

if i were in your place, i would go for

1.Integer.parseInt(String intValue); [or]
2. Integer.valueOf(String intValue).intValue();

[Harshit Rastogi]

 

return type of the valueOf is wrapper(Integer) .

if jdk1.5 is used it doesnt matter because of autoboxing

[Seetharaman Venkatasamy]

 

Harshit Rastogi wrote:if jdk1.5 is used it doesnt matter because of autoboxing

yes. true...

[Rob Spoor]

Still, Integer.parseInt is more efficient because it doesn't create a new Integer object, which Integer.valueOf will do.

[Jesper de Jong]

 

Rob Prime wrote:Still, Integer.parseInt is more efficient because it doesn't create a new Integer object, which Integer.valueOf will do.

The method Integer.valueOf(int i) uses a cache if i is between -128 and 127, so it doesn't create a new object if the value is between those boundaries. So I thought you were incorrect when you said that Integer.valueOf(String s) always creates a new object. I checked out the source code of class Integer (available in src.zip in the JDK directory), and to my surprise saw this:

public static Integer valueOf(String s) throws NumberFormatException
{
return new Integer(parseInt(s, 10));
}

So indeed, the method that takes a String always creates a new Integer object - you were right.

I wonder why this is - why did the people who programmed the JDK not write it like this?

public static Integer valueOf(String s) throws NumberFormatException
{
return valueOf(parseInt(s, 10));
}

Strange! But you know, the standard Java library isn't perfect...