学习笔记

来源：https://coding.imooc.com/learn/list/207.html

玩转数据结构

public class Array5 {

    private int[] data;
    private int size;

    // 构造函数，传入数组的容量capacity构造Array
    public Array5(int capacity) {
        data = new int[capacity];
        size = 0;
    }

    // 无参数的构造函数，默认数组的容量capacity=10
    public Array5() {
        this(10);
    }

    // 获取数组的容量
    public int getCapacity() {
        return data.length;
    }

    // 获取数组中的元素个数
    public int getSize() {
        return size;
    }

    // 返回数组是否为空
    public boolean isEmpty() {
        return size == 0;
    }

    // 向所有元素后添加一个新元素
    public void addLast(int e) {
        add(size, e);
    }

    // 在所有元素前添加一个新元素
    public void addFirst(int e) {
        add(0, e);
    }

    // 在index索引的位置插入一个新元素e
    public void add(int index, int e) {

        if (size == data.length)
            throw new IllegalArgumentException("Add failed. Array is full.");

        if (index < 0 || index > size)
            throw new IllegalArgumentException("Add failed. Require index >= 0 and index <= size.");

        for (int i = size - 1; i >= index; i--)
            data[i + 1] = data[i];

        data[index] = e;

        size++;
    }

    // 获取index索引位置的元素
    public int get(int index) {
        if (index < 0 || index >= size)
            throw new IllegalArgumentException("Get failed. Index is illegal.");
        return data[index];
    }

    // 修改index索引位置的元素为e
    public void set(int index, int e) {
        if (index < 0 || index >= size)
            throw new IllegalArgumentException("Set failed. Index is illegal.");
        data[index] = e;
    }

    // 查找数组中是否有元素e
    public boolean contains(int e) {
        for (int i = 0; i < size; i++) {
            if (data[i] == e)
                return true;
        }
        return false;
    }

    // 查找数组中元素e所在的索引，如果不存在元素e，则返回-1
    public int find(int e) {
        for (int i = 0; i < size; i++) {
            if (data[i] == e)
                return i;
        }
        return -1;
    }

    // 从数组中删除index位置的元素, 返回删除的元素
    public int remove(int index) {
        if (index < 0 || index >= size)
            throw new IllegalArgumentException("Remove failed. Index is illegal.");

        int ret = data[index];
        for (int i = index + 1; i < size; i++)
            data[i - 1] = data[i];
        size--;
        return ret;
    }

    // 从数组中删除第一个元素, 返回删除的元素
    public int removeFirst() {
        return remove(0);
    }

    // 从数组中删除最后一个元素, 返回删除的元素
    public int removeLast() {
        return remove(size - 1);
    }

    // 从数组中删除元素e
    public void removeElement(int e) {
        int index = find(e);
        if (index != -1)
            remove(index);
    }

    @Override
    public String toString() {

        StringBuilder res = new StringBuilder();
        res.append(String.format("Array: size = %d , capacity = %d\n", size, data.length));
        res.append('[');
        for (int i = 0; i < size; i++) {
            res.append(data[i]);
            if (i != size - 1)
                res.append(", ");
        }
        res.append(']');
        return res.toString();
    }
}

Test

public class Main5 {

    public static void main(String[] args) {

        Array5 arr = new Array5(20);
        for (int i = 0; i < 10; i++)
            arr.addLast(i);
        System.out.println(arr);

        System.out.println("--------------------------------");

        arr.add(1, 100);
        System.out.println(arr);

        System.out.println("--------------------------------");

        arr.addFirst(-1);
        System.out.println(arr);
        // [-1, 0, 100, 1, 2, 3, 4, 5, 6, 7, 8, 9]

        System.out.println("--------------------------------");
        arr.remove(2);
        System.out.println(arr);

        System.out.println("--------------------------------");

        arr.removeElement(4);
        System.out.println(arr);

        System.out.println("--------------------------------");
        arr.removeFirst();
        System.out.println(arr);
    }
}

Sout

Array: size = 10 , capacity = 20
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
--------------------------------
Array: size = 11 , capacity = 20
[0, 100, 1, 2, 3, 4, 5, 6, 7, 8, 9]
--------------------------------
Array: size = 12 , capacity = 20
[-1, 0, 100, 1, 2, 3, 4, 5, 6, 7, 8, 9]
--------------------------------
Array: size = 11 , capacity = 20
[-1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
--------------------------------
Array: size = 10 , capacity = 20
[-1, 0, 1, 2, 3, 5, 6, 7, 8, 9]
--------------------------------
Array: size = 9 , capacity = 20
[0, 1, 2, 3, 5, 6, 7, 8, 9]