String Class Help

Guys how would I go about doing the following. Say I wanted to find the length of a string using the length() method, eg. int get = str.length();
And then say if the length of the string is more than 7 characters, use only the first 7 characters using the method substring.
I thought if you started beginning of index is 0 and end of index is 7, it would print a new string from index 0-7, but can't get it to work.
Help appreciated.

Ill take a stab at what i think your having trouble with, hard to say without any code snippet, but this extends on my first post about String being immutable
String s = "hellomynameisjimmybopandimadumbwhiteguy";
s.substring(0, 7); //s is unchanged
String s = "hellomynameisjimmybopandimadumbwhiteguy";
s = s.substring(0, 7); //s is now changed

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How to implement the String class "split()" method (JDK1.4) in JDK 1.3

is it possible , with some code, to implement the split() method of the String class......which is added in JDK1.4 ..... in JDK1.3
would be helpful if anyone could suggest some code for this...

Here it is
public static String[] split(String source, char separ){
answer=new Vector();
int position=-1, newPosition;
while ((newPosition=source.indexOf(separ,position+1))>=0){
answer.add(source.subString(position+1,newPosition));
position=newPosition;
} //while
answer.add(source.subString(position+1,source.length-1);
return (String[])(answer.toArray());
} //split

What does the trim() method of the String class do in special cases?

Looking here ( String (Java Platform SE 7 ) ), I understand that the trim() method of the String class "returns a copy of the string, with leading and trailing whitespace omitted", but I don't understand what the last special case involving Unicode characters is exactly.
Looking here ( List of Unicode characters - Wikipedia, the free encyclopedia ), I see that U+0020 is a space character, and I also see the characters that follow the space character (such as the exclamation mark character).
So, I decided to write a small code sample to try and replicate the behaviour that I quoted (from the API documentation of the trim method) in the multi-line comment of this same code sample. Here is the code sample.:
public class TrimTester {
    public static void main(String[] args) {
         * "Otherwise, let k be the index of the first character in the string whose code
         * is greater than '\u0020', and let m be the index of the last character in the
         * string whose code is greater than '\u0020'. A new String object is created,
         * representing the substring of this string that begins with the character at
         * index k and ends with the character at index m-that is, the result of
         * this.substring(k, m+1)."
        String str = "aa!Hello$bb";
        System.out.println(str.trim());
However, what is printed is "aa!Hello$bb" (without the quotes) instead of "!Hello$" (without the quotes).
Any input to help me better understand what is going on would be greatly appreciated!

That's not what I was thinking; I was thinking about the special case where the are characters in the String whose Unicode codes are greater than \u0020.
In other words, I was trying to trigger what the following quote talks about.:
Otherwise, let k be the index of the first character in the string whose code is greater than '\u0020', and let m be the index of the last character in the string whose code is greater than '\u0020'. A new String object is created, representing the substring of this string that begins with the character at index k and ends with the character at index m-that is, the result of this.substring(k, m+1).
Basically, shouldn't the String returned be the String that is returned by the String class' substring(3,9+1) method (because the '!' and '$' characters have a Unicode code greater than \u0020)?
It seems to not be the case, but why?

The TableModel.getColumnClass() always return String class

Hi, anybody here has ever encountered and problem like mine? Please help if you do.
I have an JTable and the table model derived from AbstractTableModel, I use TableSorter from the tutorial to sort the table(I have also implemented my own sorting method, but the result is the same), but whatever the data type of the table column, the getColumnClass() method always return String type, so the table is always sorted by String type.
My implementation of this method is as following:
return getValueAt(0, columnIndex).getClass();
What is possibly wrong?
Please help, thank you so much!
Janet

Presumably the data in your first cell is a String object... therefore your code in getColumnClass() will always return String.class.

String Methods Help Please~```

Hi, I have a question that goes like this:
Write a Java class called KillWhiteSpace, which defines a main() method that asks the user to enter a String s, and displays a new String consisting of all the characters in s, but with the leading and trailing white space removed. In addition, every sequence of spaces within the String is reduced to one space only. You MUST NOT use any methods defined in the String class other than charAt() and length().
So far, I wrote
import java.until.Scanner;
public class KillWhiteSpace{
public static void main(String args[]){
System.out.println("Please enter a bunch of texts");
Scanner keyboard=new Scanner(System.in);
String w=keyboard.nextLine();
Now I know what charAt() and length() does but I don't know how to use it to satisfy the requirements above. Any helps?
Edited by: Lillian_Cao on Oct 20, 2008 8:17 PM

I don't want to give you too much since this is clearly an educational exercise, but to get you going, it looks like you you want to iterate over all the characters in the string, analyze each one, keeping track of previous characters and construct your new string as you go.
Good luck and have fun.

String.class without split(String regex)

hello,
This is my problem:
I am using eclipse with j2sdk1.4.2 which
implement
the clase String.class with
method replaceAll(String regex, String replacement) and
method split(String regex)
PAth: home_j2sdk1.4.2/jre/lib/rt.jar 25.762kb
In this way:
String columns[] = line.split("\t");
for (int i=0; i<columns.length; i++)
ws.addCell(new Label(i,row,columns.replaceAll("\"","")));
I move the code above to websphere Application Developer 5.1.2
which use Home_Websphere/eclipse/jre/lib/rt.jar 8.827 kb
this jar in yours String.class not contains the
method replaceAll(String regex, String replacement) and
method split(String regex)
I need to find the use my code above with that methods,
what i need to do ???
possible,i need to find the source to String.java of j2sdk1.4.2
which implement the methods, but where ???
or there is another way to do it ???
Any help is greatly appreciated.

If websphere is supposedly 1.4 compatible, arethey
"allowed" to leave out methods from the JFC? Not sure what the JFC is, but no, they would not be
allowed to leave out any methods.
JFC - Java Foundation Classes. I think they started calling what might be considered the Java Core the JFC when they first added Swing to the distribution. Maybe the term is no longer used.
RRD-R
� {�

Converting a long to a string (PLEASE HELP)

I am trying to convert a long to a string so that I can put it into a vector. I have this:
long fileSize = 0;
String fileModDate = null;
Vector fileList = new Vector();
~~~~~~~
File [] files = myDir.listFiles();
for (int i = 0; i<files.length; i++){
fileSize = files.length();
String s = fileSize.toString();
//do the same for the mod date
fileModDate = files[i].lastModified();
When i try this, i get an error that long can not be dereferenced. Can anyone please help?

There are two ways to solve this problem. You are trying to convert a primative type to a string without using its wrapper function (Long). So if you created a long variable as a (Long) object you could call its toString() method and this would work...
The other way is to simply use the static method in the String class valueOf(long) as follows:
String longString = String.valueOf(i);Hope this helps.
Mark

NSAPI, C++ and the STL string class

Hi,
I have a NSAPI service function written in C, but I would like to use C++ in order to take advantage of the STL string class. I am using NSAPI 4.1 and Solaris 8 and compiling with gcc 3.2. Everything compiles fine, but when I start the server, I get an error message stating that symbol _ZNSaIcED1Ev can not be found.
Any help would be greatly appreciated.
Thanks,
Mike

Well, I assume that you are trying to write a Native method. In this case, both the input string and the output string are jstrings. To operate on them in C you will have to convert them to c-strings - probably null-terminated strings.
The JNI documentation includes discussions of jstrings and conversion methods.

Extend the String Class

Is there a way to extend the string class? I know it's final, if i make my class final too would that work? I want to add some functionality to the string class, but I wanna be able to do concatination with the + operator and stuff like that. That's special to the String class.
Any help would be great.
Thanks.
Joe

Well, put your mind at easy with the fact that being
able to use the '+' operator on Strings is a design
flaw in Java. At least from a purist point of view...And from a pragmatist's point of view, it's a reasonable compromise, the benefit of which outweighs the downside. This is consistent with Java's goal as a good general-purpose language. It's not intended to be pure OO or pure anything else.

How does the String class achieve this.

How come we can do the following with the String class:
// The class is initialized using the equals sign!
String s = "Hello, World"";I am currently checking the string class but can not find what makes the above possible. could anyone help me?

ok sorry for not being so clear :)
When having a String class, we can initialize it by doing the following:
String myString = "Hello World"; Whis as JosAH explained it is handeled by the compiler. However my common sense tells me that the String class is nothing but a normal class (not like int, long, etc). So if it a normal class, then in that class there is a way to understand what = "somthing" means, and update it's state accordingly.
I would like to do the same think with my class. example:
Person MyPerson = "John, Smith";The above is a stupid example, however it gathers my point. The String class sess what is inside the quates and updates it state (with the help of the compiler). Can the Person class do the same? how?

Doubt with String class

Please tell me why String class objects are immutable. Why it was designed like that?

Read Java tutorials.Thanks for your reply. But tutorial says thatString
objects are immutable but they dont say why
they
made
as immutable.Welcome swathi.reply #4 is the best answer Ithink.
But please look at my reply #8Please look at reply#2 in the other thread.But reply #2 was mine. I dont understand what you say? Please help me.

Problems with String[] Class Object

Hi guys,
I'm writing a web server who should invoke a method of a class when asked by a client.
My problem is that if the method that should be invoked has a String[] parameter the web server is unable to invoke it and throws a java.lang.IllegalArgumentException: argument type mismatch.
Useful pieces of code to understand are the following:
//create the Class[] to pass as parameter to the getMethod method
Class[] paramType = {String[].class};
//find the class "className" and create a new instance
Class c = Class.forName(className);
Object obj = c.newInstance();
//the getMethod should find in the class c the method called nameMeth
// having paramType (i.e. String[]) as parameter type...
Method theMethod = c.getMethod(nameMeth, paramType);
//here's the problematic call!!
theMethod.invoke(obj, params);I've noted that System.out.println(theMethod); prints the signature of the method with the parameter type java.lang.String[].
System.out.println(paramType[0]); instead prints [Ljava.lang.String;
I know that [L means that it is an array, so why do you think that I'm having an argument type mismatch?
Thank you

I had no problems making that work.import java.lang.reflect.Method;
public final class StringArray {
    public static final String CLASSNAME = "StringArray";
    public static final String METHODNAME = "myMethod";
    public static final String[] sa = { "a", "b"};
    // automatic no-args constructor
    public final void myMethod(String[] sa) {
        for(int i=0;i<sa.length;++i) {
            System.out.println(sa);
public static final void main(String[] arg) throws Exception {
//create the Class[] to pass as parameter to the getMethod method
Object[] params = { sa };
Class[] paramType = {sa.getClass()};
//find the class "className" and create a new instance
Class c = Class.forName(CLASSNAME);
Object obj = c.newInstance();
//the getMethod should find in the class c the method called nameMeth
// having paramType (i.e. String[]) as parameter type...
Method theMethod = c.getMethod(METHODNAME, paramType);
//here's the problematic call!!
theMethod.invoke(obj, params);

How to find out what are the functions supported by string class

Hi,
Can any one let me know how to find what are all the functions supported by the string class in standard(STL) library on solaris.
Regards,
Vignesh

1. Any C++ textbook that covers the Standard Library will tell you about the standard string class. A good tutorial and reference for the entire Standard Library is "The C++ Standard Library" by Nicolai Josuttis, published by Addison Wesley.
2. WIth Sun C++, the command
man -s3C++ basic_string
provides documentation for the default libCstd version of the Standard Library.
3. You could look at the <string> header itself. I don't recommend that approach.

Memory leak in string class

We have developed our application in Solaris 10 environment. While running Purify on that it shows leak in the string class. This leak is incremental and so process size keeps in increasing. If we replace string with char array, the leaks disappears and process size also becomes stable.
Following is the snapshot of the memory leak stack reported by Purify:
MLK: 4505 bytes leaked in 85 blocks
* This memory was allocated from:
malloc [rtlib.o]
operator new(unsigned) [libCrun.so.1]
void*operator new(unsigned) [rtlib.o]
__rwstd::__string_ref<char,std::char_traits<char>,std::allocator<char> >*std::basic_string<char,std::char_traits<char>,std::allocator<char> >::__getRep(unsigned,unsigned) [libCstd.so.1]
char*std::basic_string<char,std::char_traits<char>,std::allocator<char> >::replace(unsigned,unsigned,const char*,unsigned,unsigned,unsigned) [libCstd.so.1]
std::basic_string<char,std::char_traits<char>,std::allocator<char> >&std::basic_string<char,std::char_traits<char>,std::allocator<char> >::operator=(const char*) [libCstd.so.1]
Has anyone faced this problem earlier or is there any patch available for this?

Over time, we have found and fixed memory leaks in the C++ runtime libraries.
Get the latest patches for the compiler you are using. (You didn't say which one.) You can find all patches here:
[http://developers.sun.com/sunstudio/downloads/patches/index.jsp]
Also get the latest Solaris patch for the C++ runtime libraries, listed on the same web page.
If that doesn't fix the problem, please file a bug report at
[http://bugs.sun.com]
with a test case that can be compiled and run to demonstrate the problem.

Sort a string :: Please help.

Hello Everyone,
I am having this very simple problem of sorting a String. please help.
     static String sortString(String str){
          List list = Arrays.asList(str);
          Collections.sort(list);
          for(int i=0, n=list.size();i<n;i++){
               System.out.println(","+ list.get(i));
The function is supposed to take a String and sort it & print it out. This should be simple. Where am I making mistakes? Please help!!

Hello Everyone,
I am having this very simple problem of sorting a String. please help.
     static String sortString(String str){
          List list = Arrays.asList(str);
          Collections.sort(list);
          for(int i=0, n=list.size();i<n;i++){
               System.out.println(","+ list.get(i));
               return str;
The function is supposed to take a String and sort it & print it out. This should be simple. Where am I making mistakes? Please help!!

String Class Help

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