Question 294507 in Json Question posted in
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Json – How to get index of a string in an a list

public int userCompare(String s1, int i1, String s2, int i2){
        String[] alphabety = {"a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l", "m", "n", "o", "p", "q", "r", "s", "t", "u", "v", "w", "x", "y", "z"};
        String[] firstThing = s1.split("(?!^)");
        String[] secondThing = s2.split("(?!^)");
}

How do I complete the following:

Create a method called userCompare that will return a -1, 1, or 0 based on the following: We have data for two users, A and B, each with a String name and an int id. The goal is to order the users such as for sorting. Return -1 if A comes before B, 1 if A comes after B, and 0 if they are the same. Order first by the string names, and then by the id numbers if the names are the same.

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2

Answers


  1. 0

    I’d compare each component individually, and then use signum to get strictly 1, -1 or 0.

    public int userCompare(User a, User b) {
    int retVal = a.getName().compareTo(b.getName);
    if (retVal != 0) {
        return (int) Math.signum(retVal);
    }

    retVal = Integer.compare(a.getId(), b.getId());
    return (int) Math.signum(retVal);
}

    Side note – for the purpose of sorting in Java, you don’t need to strictly return 1, -1 or 0, you can just return an arbitrary positive, negative or zero value. In other words, the usage of signum is required by question, but isn’t strictly required for sorting.

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  2. 0

    I would utilize the String#compareTo, and Integer#compare methods here.

    int userCompare(String nameA, int idA, String nameB, int idB) {
    int t;
    if ((t = nameA.compareTo(nameB)) == 0)
        return Integer.compare(idA, idB);
    return t;
}

    If you’re looking to implement the actual comparison routine, review the source for each of those methods.
    For a String, it’s just a traversal of the bytes.

    Here is utilized StringLatin1#compareTo method.
    GitHub – OpenJDK – StringLatin1.java – compareTo(byte[], byte[], int, int).

    public static int compareTo(byte[] value, byte[] other, int len1, int len2) {
    int lim = Math.min(len1, len2);
    for (int k = 0; k < lim; k++) {
        if (value[k] != other[k]) {
            return getChar(value, k) - getChar(other, k);
        }
    }
    return len1 - len2;
}

    And, for an Integer it’s just a relational, and equality, operation.
    GitHub – OpenJDK – Integer.java – compare(int, int).

    /**
 * Compares two {@code int} values numerically.
 * The value returned is identical to what would be returned by:
 * <pre>
 *    Integer.valueOf(x).compareTo(Integer.valueOf(y))
 * </pre>
 *
 * @param  x the first {@code int} to compare
 * @param  y the second {@code int} to compare
 * @return the value {@code 0} if {@code x == y};
 *         a value less than {@code 0} if {@code x < y}; and
 *         a value greater than {@code 0} if {@code x > y}
 * @since 1.7
 */
public static int compare(int x, int y) {
    return (x < y) ? -1 : ((x == y) ? 0 : 1);
}
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