课堂作业-Bag类的实现

课堂作业-Bag类的实现

要求：

1. 代码运行在命令行中，路径要体现学号信息，IDEA中，伪代码要体现个人学号信息

2. 参见Bag的UML图，用Java继承BagInterface实现泛型类Bag，并对方法进行单元测试（JUnit），测试要涵盖正常、异常情况、边界情况。

   实验思路

   0.编写接口

   1.编写伪代码

   2.实现接口

   3.使用junit进行测试

   代码编写的主要思想分析

   使用数组实现Bag类，达到可增可删可判断是否为空等等。

• 0 . 定义一个Object类型的数组，其长度为0
• 1 . 判断是否为空时只需要判断其数组的长度是否为0
• 2 . 增加新元素时，先定义一个比原来长度增加1的数组，再将原来的数组重新赋值到新的数组里面
• 3 . 删除指定元素时，先将元素的下标找出来，用for循环将指定元素后面的元素覆盖指定元素
• 4 . 获取某元素在Bag里面的数量，用线性查找便可完成
• 5 . 判断某元素在Bag是否存在，用线性查找便可

public class Bag implements BagInterface {

    private Object[] data1 = new Object[0];
    int q = 0, index;
    Object result;

    public boolean isEmpty() {
        if (data1.length != 0)
            return false;
        else
            return true;
    }

    public boolean add(Object anEntry) {
        q++;
        Object[] objects = new Object[q - 1];
        objects = sum(data1);
        data1 = new Object[q];
        for (int i = 0; i < data1.length - 1; i++) {
            data1[i] = objects[i];
        }
        data1[q - 1] = anEntry;
        return true;
    }

    public boolean remove(Object anEntry) {
        int index = linearSearch(data1, anEntry);
        for (int i = index + 1; i < data1.length; i++) {
            data1[index] = data1[i];
        }
        q--;
        Object[] objects = new Object[q + 1];
        objects = sum(data1);
        if (q <= 0)
            return true;
        else {
            data1 = new Object[q];
            for (int i = 0; i < q; i++) {
                data1[i] = objects[i];
            }
        }
        return true;
    }

    public int getCurrentSize() {
        return data1.length;
    }

    public void clear() {
        data1 = new Object[0];
    }

    public int getFrequencyOf(Object anEntry) {
        int count = 0;
        for (int i = 0; i < data1.length; i++) {
            if (anEntry == data1[i]) {
                count++;
            }
        }
        return count;
    }

    public boolean contains(Object anEntry) {
        for (int i = 0; i < data1.length; i++) {
            if (anEntry == data1[i])
                return true;
        }
        return false;
    }

    public Object[] sum(Object[] objects) {
        Object[] objects1 = new Object[objects.length];
        for (int i = 0; i < objects.length; i++) {
            objects1[i] = objects[i];
        }
        return objects1;
    }

    public static int linearSearch(Object[] data, Object target) {
        int index = 0;
        for (int i = 0; i < data.length; i++) {
            if (target == data[i]) {
                index = i;
            }
        }
        return index;
    }

    public Object[] toArray() {
        insertionSort(data1);
        return data1;
    }

    public static void insertionSort(Object[] data) {
        for (int index = 1; index < data.length; index++) {
            Object key = data[index];
            int position = index;
            // Shift larger values to the right
            while (position > 0 && data[position - 1].equals(key)) {
                data[position] = data[position - 1];
                position--;
            }
            data[position] = key;
        }
    }
}

junit测试

import junit.framework.Test;
import junit.framework.TestSuite;
import junit.framework.TestCase;

import static org.junit.Assert.assertEquals;

/**
 * Bag Tester.
 *
 * @author <Authors name>
 * @version 1.0
 * @since <pre>09/25/2017</pre>
 */
public class BagTest extends TestCase {

    public BagTest(String name) {
        super(name);
    }

    public void setUp() throws Exception {
        super.setUp();
    }

    public void tearDown() throws Exception {
        super.tearDown();
    }

    /**
     * Method: isEmpty()
     */
    public void testIsEmpty() throws Exception {
//TODO: Test goes here...
        assertEquals(true, new MyArrayList().isEmpty());
    }

    /**
     * Method: add(Object anEntry)
     */
    public void testAdd() throws Exception {
//TODO: Test goes here...
        MyArrayList bag = new MyArrayList();
        bag.add(1);
        assertEquals(true, bag.add(5));
    }
    @org.junit.Test
    public void testremove() throws Exception {
        MyArrayList bag = new MyArrayList();
        bag.add(7);
        bag.add(4);
        assertEquals(true, bag.remove(4));
    }

    @org.junit.Test
    public void testgetCurrentSize() throws Exception{
        MyArrayList bag = new MyArrayList();
        bag.add(1);
        bag.add(3);
        assertEquals(2,bag.getCurrentSize());

    }

    @org.junit.Test
    public void testcontains() throws Exception{
        MyArrayList bag = new MyArrayList();
        bag.add(1);
        bag.add(3);
        assertEquals(false, bag.contains(2));
    }
}