utils/src/main/java/jetbrains/exodus/core/dataStructures/hash/HashSet.java [54:96]:
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        if (key == null) {
            return holdsNull;
        }

        final Entry<E>[] table = this.table;
        final int hash = key.hashCode();
        final int index = HashUtil.indexFor(hash, table.length, mask);

        for (Entry<E> e = table[index]; e != null; e = e.hashNext) {
            final E entryKey;
            if ((entryKey = e.key) == key || entryKey.equals(key)) {
                return true;
            }
        }

        return false;
    }

    @Override
    public boolean add(E key) {
        if (key == null) {
            final boolean wasHoldingNull = holdsNull;
            holdsNull = true;
            if (!wasHoldingNull) {
                size += 1;
            }
            return !wasHoldingNull;
        }

        final Entry<E>[] table = this.table;
        final int hash = key.hashCode();
        final int index = HashUtil.indexFor(hash, table.length, mask);

        for (Entry<E> e = table[index]; e != null; e = e.hashNext) {
            final E entryKey;
            if ((entryKey = e.key) == key || entryKey.equals(key)) {
                return false;
            }
        }

        final Entry<E> e = new Entry<>(key);
        e.hashNext = table[index];
        table[index] = e;
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utils/src/main/java/jetbrains/exodus/core/dataStructures/hash/LinkedHashSet.java [56:98]:
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        if (key == null) {
            return holdsNull;
        }

        final Entry<E>[] table = this.table;
        final int hash = key.hashCode();
        final int index = HashUtil.indexFor(hash, table.length, mask);

        for (Entry<E> e = table[index]; e != null; e = e.hashNext) {
            final E entryKey;
            if ((entryKey = e.key) == key || entryKey.equals(key)) {
                return true;
            }
        }

        return false;
    }

    @Override
    public boolean add(E key) {
        if (key == null) {
            final boolean wasHoldingNull = holdsNull;
            holdsNull = true;
            if (!wasHoldingNull) {
                size += 1;
            }
            return !wasHoldingNull;
        }

        final Entry<E>[] table = this.table;
        final int hash = key.hashCode();
        final int index = HashUtil.indexFor(hash, table.length, mask);

        for (Entry<E> e = table[index]; e != null; e = e.hashNext) {
            final E entryKey;
            if ((entryKey = e.key) == key || entryKey.equals(key)) {
                return false;
            }
        }

        final Entry<E> e = new Entry<>(key);
        e.hashNext = table[index];
        table[index] = e;
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