배열 인덱스와 삽입 비용

import java.util.Arrays;

public final class ArrayInsertOverwriteBug {
    public static void main(String[] args) {
        String[] titles = {"array", "list", null, null};
        int size = 2;
        int index = 0;
        for (int i = index; i < size; i++) {
            titles[i + 1] = titles[i];
        }
        titles[index] = "index";
        size++;
        System.out.println(Arrays.toString(Arrays.copyOf(titles, size)));
    }
}

[index, array, array]

import java.util.Arrays;

public final class ArrayIndexOperations {
    public static void main(String[] args) {
        TitleArray titles = new TitleArray(5);
        titles.add("array");
        titles.add("list");
        titles.add(1, "index");
        System.out.println(titles.get(1));
        System.out.println("found=" + titles.indexOf("list"));
        System.out.println("removed=" + titles.remove(0));
        System.out.println(titles);
    }

    private static final class TitleArray {
        private final String[] values;
        private int size;

        TitleArray(int capacity) {
            values = new String[capacity];
        }

        void add(String value) {
            add(size, value);
        }

        void add(int index, String value) {
            checkAddIndex(index);
            if (size == values.length) throw new IllegalStateException("full");
            for (int i = size - 1; i >= index; i--) {
                values[i + 1] = values[i];
            }
            values[index] = value;
            size++;
        }

        String get(int index) {
            checkElementIndex(index);
            return values[index];
        }

        int indexOf(String target) {
            for (int i = 0; i < size; i++)
                if (java.util.Objects.equals(values[i], target)) return i;
            return -1;
        }

        String remove(int index) {
            checkElementIndex(index);
            String old = values[index];
            for (int i = index + 1; i < size; i++) {
                values[i - 1] = values[i];
            }
            values[--size] = null;
            return old;
        }

        private void checkElementIndex(int index) {
            if (index < 0 || index >= size) throw new IndexOutOfBoundsException(index);
        }

        private void checkAddIndex(int index) {
            if (index < 0 || index > size) throw new IndexOutOfBoundsException(index);
        }

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

public final class PostRepositoryCliCH141 {
    public static void main(String[] args) {
        PostRepository repository = new PostRepository();
        repository.add("array-index", 35);
        repository.add("insert-shift", 45);
        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) {}
}