Go Premium for a chance to win a PS4. Enter to Win

x
?
Solved

lastIndexOf method in java

Posted on 2014-12-02
7
Medium Priority
?
409 Views
Last Modified: 2014-12-02
public class Test35 {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		// TODO Auto-generated method stub

		String string="aabbzzzwexrweyyywexooo";//wex is at index 7 and 16
	    System.out.println("string.indexOf(\"wex\",5) -> " + string.indexOf("wex",5));
	    System.out.println("string.indexOf(\"wex\",9) -> " + string.indexOf("wex",9));
	      System.out.println("string.indexOf(\"wex\",string.indexOf(\"wex\",5)+2) -> " + string.indexOf("wex",string.indexOf("wex",5)+2) ); 
	    System.out.println("string.lastIndexOf(\"wex\",16)  ->  " + string.lastIndexOf("wex",16));
	    System.out.println("string.lastIndexOf(\"wex\",11)  -> " + string.lastIndexOf("wex",11));
	    System.out.println("string.lastIndexOf(\"wex\",7)  -> " + string.lastIndexOf("wex",7));
                          System.out.println("string.lastIndexOf(\"wex\",15)  -> " + string.lastIndexOf("wex",15));
                          System.out.println("string.lastIndexOf(\"wex\",17)  -> " + string.lastIndexOf("wex",17));
	}

	
}

                    

Open in new window


i wrote my program as above and got below output


string.indexOf("wex",5) -> 7
string.indexOf("wex",9) -> 16
string.indexOf("wex",string.indexOf("wex",5)+2) -> 16
string.lastIndexOf("wex",16)  ->  16
string.lastIndexOf("wex",11)  -> 7
string.lastIndexOf("wex",7)  -> 7
string.lastIndexOf("wex",15)  -> 7
string.lastIndexOf("wex",17)  -> 16


I as not clear on output


string.lastIndexOf("wex",16)  ->  16
string.lastIndexOf("wex",11)  -> 7
string.lastIndexOf("wex",7)  -> 7
string.lastIndexOf("wex",15)  -> 7
string.lastIndexOf("wex",17)  -> 16

How and why it came for lastIndexOf().

Please advise
0
Comment
Question by:gudii9
  • 3
  • 2
  • 2
7 Comments
 
LVL 85

Assisted Solution

by:ozo
ozo earned 1000 total points
ID: 40476157
"wex" appears at positions 7 and 16 in string, so
string.lastIndexOf("wex",X) == 16 when 16<=X
string.lastIndexOf("wex",X) == 7 when 7<=X && X<16
string.lastIndexOf("wex",X) == -1 when  X<7
0
 
LVL 32

Accepted Solution

by:
awking00 earned 1000 total points
ID: 40476782
lastIndexOf with 2 parameters (a search string and an index) searches backwards from the index to find the search string.


string.lastIndexOf("wex",16)  ->  16 => OK - Search started at 16 and immediately found "wex"
string.lastIndexOf("wex",11)  -> 7 => OK - Search started at 11, then went to 10, then 9,  then 8,  then 7 and  found "wex"
string.lastIndexOf("wex",7)  -> 7 => OK - Search started at 7 and immediately found "wex"
string.lastIndexOf("wex",15)  -> 7 OK - Search started at 15, then 14, then 13,  then 12,  then 11, then 10, then 9,  then 8,  then 7 and  found "wex"
string.lastIndexOf("wex",17)  -> 16 => OK - Search started at 17, then went to 16 and  found "wex"
0
 
LVL 85

Expert Comment

by:ozo
ID: 40476847
string.lastIndexOf( str,fromIndex) <= Math.max(fromIndex,-1)

string.lastIndexOf( str,fromIndex) returns the largest value k for which:
     k <= fromIndex && string.startsWith(str, k)

If no such value of k exists, then -1 is returned.
0
Concerto's Cloud Advisory Services

Want to avoid the missteps to gaining all the benefits of the cloud? Learn more about the different assessment options from our Cloud Advisory team.

 
LVL 7

Author Comment

by:gudii9
ID: 40476939
now lastIndexOf() makes sense.

Similar too how we are calling lastIndexOf() the indexOf() also should be called something like firstIndexOf() since it is finding first occurence index of the target.

Please advise
0
 
LVL 32

Expert Comment

by:awking00
ID: 40476965
I don't know that indexOf should be called firstIndexOf, but you can cetainly think of it that way.
0
 
LVL 7

Author Comment

by:gudii9
ID: 40476970
yea
0
 
LVL 85

Expert Comment

by:ozo
ID: 40476991
You can define your own methods If you want,
but when other people read your code they may not be as familiar as the standard methods,
so you should document them at least as clearly as the standard methods,
and be sure that the clarity they add to your code is worth the extra effort to learn your non-standard methods.
0

Featured Post

Free Tool: ZipGrep

ZipGrep is a utility that can list and search zip (.war, .ear, .jar, etc) archives for text patterns, without the need to extract the archive's contents.

One of a set of tools we're offering as a way to say thank you for being a part of the community.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

In real business world data are crucial and sometimes data are shared among different information systems. Hence, an agreeable file transfer protocol need to be established.
Make the most of your online learning experience.
This tutorial covers a practical example of lazy loading technique and early loading technique in a Singleton Design Pattern.
How to fix incompatible JVM issue while installing Eclipse While installing Eclipse in windows, got one error like above and unable to proceed with the installation. This video describes how to successfully install Eclipse. How to solve incompa…
Suggested Courses

963 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question