org.javimmutable.collections.cursors.Cursors Maven / Gradle / Ivy

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package org.javimmutable.collections.cursors;

import org.javimmutable.collections.Cursor;

public final class Cursors
{
    private Cursors()
    {
    }

    /**
     * Computes a hash code from the hash codes of all values in the cursor.
     *
     * @param cursor
     * @return
     */
    public static int computeHashCode(Cursor cursor)
    {
        int answer = 0;
        for (cursor = cursor.start(); cursor.hasValue(); cursor = cursor.next()) {
            Object value = cursor.getValue();
            answer = 31 * answer + ((value != null) ? value.hashCode() : 0);
        }
        return answer;
    }

    /**
     * Return true if and only if both cursors have the same length and contain objects
     * that are equal based on their equals() methods.
     *
     * @param a
     * @param b
     * @return
     */
    public static boolean areEqual(Cursor a,
                                   Cursor b)
    {
        a = a.start();
        b = b.start();
        while (a.hasValue() && b.hasValue()) {
            Object av = a.getValue();
            Object bv = b.getValue();
            if (av == null) {
                if (bv != null) {
                    return false;
                }
            } else if (bv == null) {
                return false;
            } else if (!av.equals(bv)) {
                return false;
            }
            a = a.next();
            b = b.next();
        }
        return a.hasValue() == b.hasValue();
    }

    public static String makeString(Cursor cursor)
    {
        StringBuilder sb = new StringBuilder();
        sb.append("[");
        for (cursor = cursor.start(); cursor.hasValue(); cursor = cursor.next()) {
            if (sb.length() > 1) {
                sb.append(",");
            }
            Object value = cursor.getValue();
            if (value == null) {
                sb.append("null");
            } else {
                sb.append(value);
            }
        }
        sb.append("]");
        return sb.toString();
    }
}