我的Java代码错误

Question

I've got a problem with my Java program. There is an error in my code on line 16 ( t = T[i]; ) which implies an error on line 12. It says :

Syntax error on token "=",VariableInitializer expected after this token.

Could I have some help ?

public class Ngrams {

    public static boolean estPrefixe(String t, String s) {
        int Longs = s.length();
        if (t.substring(0, Longs) == s) {
            return true;
        } else {
            return false;
        }
    }

    public static int nbOccurences(String[] T, String s) {
        int compteur = 0;
        String t = null;
        for (int i = 0; i < T.length; i++) {
            t = T[i];
            if (estPrefixe(t, s)) {
                compteur++;
            }
            return compteur;
        }
    }

Answer 1

Notwithstanding the fact that you're comparing Strings with == instead of .equals() , and that a right bracket seems to have gone AWOL, at the end of your program, you're "missing" a return statement in nbOccurences . Even though you have one in the for-loop, if you never enter the loop, you don't return anything.

Move your return statement down one line, outside of the loop instead.

public static int nbOccurences(String[] T, String s) {
    int compteur = 0;
    String t = null;
    for (int i = 0; i < T.length; i++) {
        t = T[i];
        if (estPrefixe(t, s)) {
            compteur++;
        }
    }
    return compteur;
}

Answer 2

The method nbOccurences does not always return an int value. If T is null or empty (length = 0) no value is returned. So you should add another return statement after the for loop.

As others mentioned already you should use equals to compare strings. This however, is not producing a syntax error.

Answer 3

Well there's a serious bug in this line:

if (t.substring(0, Longs) == s) {

This test will always be false, because == compares object references, not values. Change it to:

if (t.substring(0, Longs).equals(s)) {

But the whole method is pointless. Change it to:

public static boolean estPrefixe(String t, String s) {
    return t.startsWith(s);
}

Or just delete the method altogether because it adds no value whatsoever.