So I'm having trouble with an assignment where I need to return the first or second token of a string, based on the given argument, using the stringtokenizer constructs and methods. EX: "3+5", 2. the return on this should be 5. Now what I have so far is:
StringTokenizer st = new StringTokenizer (input, "+-*/%");
if (st.hasMoreTokens());
return st.nextToken();
this returns the first token of the string, but im unsure of how to return the second token. any advice?
if (st.hasMoreTokens());
Should be
if (st.hasMoreTokens())
There is an extra ;, With that extra ; your code like writing,
if(..)
{
}
return st.nextToken();
Edit :
Moreover you need to form a string and then return. Not return st.nextToken(); that terminates your loop and returns the first value.
This will help you. For this program to work, we need two parameters - Input String, position of the wanted token. In the below program, I have hard coded the position of the
wanted token as '3'. so, the output would be '10', since it is the third token of the input string - 3+5*10*12+11
public static void main(String[] args) {
//input string
String input = "3+5*10*12+11";
// number of token we need
int wantedToken = 3;
// token number defaults to '1' and keeps track of the token position
int i = 1;
StringTokenizer st = new StringTokenizer(input, "+-*/%");
while (st.hasMoreTokens()) {
//when i equals wanted token, print it
if (i == wantedToken) {
System.out.println("wanted token : " + st.nextToken());
break;
}
else {
//move to next token
st.nextToken();
//increment the token position
i++;
}
}
}
Output:
run:
wanted token : 10
BUILD SUCCESSFUL (total time: 0 seconds)
Update: Converted the above code - a Seperate Method. The below code takes input string and wanted token from user
public class WantedTokenTest {
public static void main(String[] args) {
//input string
String input = null;
// number of token we need
int wantedToken = 1;
Scanner scr = new Scanner(System.in);
System.out.println("Please enter the input string : ");
input = scr.nextLine();
System.out.println("Please enter the wanted token : ");
wantedToken = scr.nextInt();
System.out.println(getWantedToken(input, wantedToken));
}
private static String getWantedToken(String input,int wantedToken){
// token number defaults from '1' and keeps track of the token position
int i = 1;
StringTokenizer st = new StringTokenizer(input, "+-*/%");
while (st.hasMoreTokens()) {
//when i equals wanted token, print it
if (i == wantedToken) {
return st.nextToken();
}
else {
//move to next token
st.nextToken();
//increment the token position
i++;
}
}
return null;
}
}
Hope, it clarifies how to do it
you can use like this while(st.hasMoreTokens()) { /... }
If you want to parse math expression with Tokenizer you should do it dinamically. You could take a look at answer1 and answer2.
But if you just want to get the second token try this code:
public static List<String> getTokens(String input) {
List<String> tokens = new ArrayList<String>();
StringTokenizer st = new StringTokenizer(input, "+-*/%");
while (st.hasMoreTokens()) {
tokens.add(st.nextToken());
}
return tokens;
}
public static void main(String[] args) {
List tokens = getTokens("3+5");
System.out.println(tokens.get(0));
System.out.println(tokens.get(1));//the second token
}
OR
public static String[] getTokens (String input) {
return input.split("[-\\+\\*\\\\]");
}
public static void main(String[] args) {
String[] tokens = getTokens("3+5");
System.out.println(tokens[0]);
System.out.println(tokens[1]);//the second token
}
