동적 배열의 용량 정책

public final class FixedCapacityOverflowFailure {
    public static void main(String[] args) {
        String[] values = new String[2];
        int size = 0;
        values[size++] = "array";
        values[size++] = "list";
        values[size++] = "growth";
    }
}

java.lang.ArrayIndexOutOfBoundsException

import java.util.Arrays;

public final class DynamicTitleList {
    public static void main(String[] args) {
        MyArrayList<String> list = new MyArrayList<>(1);
        list.add("array");
        list.add("growth");
        list.add("copy");
        System.out.println(list);
        System.out.println("size=" + list.size() + ", capacity=" + list.capacity());
    }

    private static final class MyArrayList<E> {
        private Object[] values;
        private int size;

        MyArrayList(int initialCapacity) {
            if (initialCapacity < 0) throw new IllegalArgumentException("capacity");
            values = new Object[initialCapacity];
        }

        void add(E value) {
            ensureCapacity(size + 1);
            values[size++] = value;
        }

        @SuppressWarnings("unchecked")
        E get(int index) {
            if (index < 0 || index >= size) throw new IndexOutOfBoundsException(index);
            return (E) values[index];
        }

        private void ensureCapacity(int required) {
            if (required <= values.length) return;
            int doubled = values.length == 0 ? 1 : values.length * 2;
            values = Arrays.copyOf(values, Math.max(doubled, required));
        }

        int size() {
            return size;
        }

        int capacity() {
            return values.length;
        }

        public String toString() {
            return Arrays.toString(Arrays.copyOf(values, size));
        }
    }
}

public final class PostRepositoryCliCH142 {
    public static void main(String[] args) {
        PostRepository repository = new PostRepository();
        repository.add("capacity", 30);
        repository.add("array-copy", 50);
        repository.print();
        System.out.println("total=" + repository.totalViewCount());
    }

    private static final class PostRepository {
        private Entry[] entries = new Entry[2];
        private int size;

        void add(String title, int viewCount) {
            if (title == null || title.isBlank()) throw new IllegalArgumentException("title");
            if (viewCount <= 0) throw new IllegalArgumentException("viewCount");
            ensureCapacity(size + 1);
            entries[size++] = new Entry(title, viewCount);
        }

        private void ensureCapacity(int required) {
            if (required <= entries.length) return;
            Entry[] grown = new Entry[Math.max(required, entries.length * 2)];
            System.arraycopy(entries, 0, grown, 0, size);
            entries = grown;
        }

        int totalViewCount() {
            int total = 0;
            for (int i = 0; i < size; i++) {
                total += entries[i].viewCount();
            }
            return total;
        }

        void print() {
            for (int i = 0; i < size; i++) {
                Entry entry = entries[i];
                System.out.println(i + ":" + entry.title() + "=" + entry.viewCount());
            }
        }
    }

    private record Entry(String title, int viewCount) {}
}