数据结构之数组Array_JAVA源代码及注意事项

数据结构之数组Array_JAVA

注意事项

NO.1

/*忘记加private！！！！！
数组data和数组元素个数size外界不可访问
要变为私有private
*/
private E[] data;
private int size;

NO.2

/*构造函数的写法记住
data = (E[]) new Object[Capacity]
注意：对于多类型的E
要进行类型的转换Objective------>E
*/
    public Array(int Capacity) {
        data = (E[]) new Object[Capacity];
        size = 0;
    }

NO.3

    // 在index索引的位置插入一个新元素e
    public void insert(int index,E e){
        if(index < 0 || index > size)//   错误：size == getCapacity()！！！！！！！！！
            throw new IllegalArgumentException("insert is false");
        if(size == data.length)
            resize(2 * data.length);

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

//        for (int i = data.length; i > index; i--) {
//                data[i] = data[i - 1];
//        }这里写的不对，data.length!=size
        data[index]=e;
        size++;
    }

size:数组元素的个数
.length:数组的长度
Capacity：数组的容量=长度

NO.4

/*记住抛出异常的格式
*/
if(index < 0 || index >= size)
   throw new IllegalArgumentException("Set failed. Index is illegal.");

NO.5

/*重写toString方法的格式
*/
    @Override
    public String toString(){
        StringBuilder  res = new StringBuilder();

源代码

Array类

public class Array<E> {
    private E[] data;
    private int size;

    // 构造函数，传入数组的容量capacity构造Array
    public Array(int Capacity) {
        data = (E[]) new Object[Capacity];
        size = 0;
    }
    // 无参数的构造函数，默认数组的容量capacity=10
     public Array(){
        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;
    }

    // 在index索引的位置插入一个新元素e
    public void insert(int index,E e){
        if(index < 0 || index > size)
            throw new IllegalArgumentException("insert is false");
        if(size == data.length)
            resize(2 * data.length);

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

        data[index]=e;
        size++;
    }

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

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

    // 获取index索引位置的元素
    public E 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,E 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(E e){
        for (int i = 0; i < size; i++) {
            if(data[i].equals(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(E e){
        for (int i = 0; i < size; i++) {
            if(data[i].equals(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 E delete(int index){
        if(index < 0 || index >= size)
            throw new IllegalArgumentException("Set failed. Index is illegal.");
        E temp = data[index];
        for(int i = index ; i < size - 1; i++){
                data[i]=data[i+1];
        }
        data[size-1]=null;
        size--;
        if(size == data.length / 4 && data.length / 2 != 0)
            resize(data.length / 2);
        return temp;
    }
    // 从数组中删除第一个元素, 返回删除的元素
    public E deleteFirst(){
        return delete(0);
    }

    // 从数组中删除最后一个元素, 返回删除的元素
    public E deleteLast(){
        return  delete(size-1);
    }
    // 从数组中删除元素e
    public void deleteElement(E e){
        int index=find(e);
        if(index!=-1)
        delete(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();
    }

        // 将数组空间的容量变成newCapacity大小
        private void resize(int newCapacity){

            E[] newData = (E[])new Object[newCapacity];
            for(int i = 0 ; i < size ; i ++)
                newData[i] = data[i];
            data = newData;
        }
    }

主函数main

public class main {

    public static void main(String[] args) {

        Array<Integer> arr = new Array<>();
        for(int i = 0 ; i < 10 ; i ++)
            arr.addLast(i);
        System.out.println(arr);

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

        arr.addFirst(-1);
        System.out.println(arr);

        arr.delete(2);
        System.out.println(arr);

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

        arr.deleteFirst();
        System.out.println(arr);

        for(int i = 0 ; i < 4 ; i ++){
            arr.deleteFirst();
            System.out.println(arr);
        }
    }
}

结果

"C:\Program Files\Java\jdk14\bin\java.exe" "-javaagent:C:\Program Files\JetBrains\IntelliJ IDEA 2020.2\lib\idea_rt.jar=64795:C:\Program Files\JetBrains\IntelliJ IDEA 2020.2\bin" -Dfile.encoding=UTF-8 -classpath C:\Users\12778\IdeaProjects\first\out\production\Array com.Array.main
Array : size = 10 , capacity = 10
[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]
Array : size = 8 , capacity = 20
[1, 2, 3, 5, 6, 7, 8, 9]
Array : size = 7 , capacity = 20
[2, 3, 5, 6, 7, 8, 9]
Array : size = 6 , capacity = 20
[3, 5, 6, 7, 8, 9]
Array : size = 5 , capacity = 10
[5, 6, 7, 8, 9]

Process finished with exit code 0

本文地址：https://blog.csdn.net/TOPic666/article/details/107700479