0
点赞
收藏
分享

微信扫一扫

基于SpringBoot的学生成绩管理系统

三次方 03-21 14:30 阅读 2

设计模式(行为型设计模式——迭代器模式)

迭代器模式

基本定义

模式结构

代码实现

Aggregate 抽象容器类
public interface Aggregate {

    void add(Object object);

    Object get(int index);

    int getSize();
    //获取迭代器
    Iterator iterator();
}
ConcreteAggregate 具体容器对象
@Slf4j
public class ConcreteAggregate implements Aggregate {

    private Object[] arr;
    private int size;
    private int index;
    //数据长度
    private int ARRAY_LENGTH;

    public ConcreteAggregate() {
        size = 0;
        index = 0;
        ARRAY_LENGTH = 10;
        arr = new Object[ARRAY_LENGTH];
    }

    @Override
    public void add(Object object) {
        arr[index++] = object;
        size++;
        grow();
    }
/**
* 容量自动增长
**/
    private void grow() {
        double percent = new BigDecimal(size).divide(new BigDecimal(ARRAY_LENGTH)).doubleValue();
        if(percent > 0.8){
            ARRAY_LENGTH *= 2;
            if(ARRAY_LENGTH > Integer.MAX_VALUE){
                ARRAY_LENGTH = Integer.MAX_VALUE;
            }
            Object[] newArr = new Object[ARRAY_LENGTH];
            System.arraycopy(arr, 0, newArr, 0, size);
            arr = newArr;
        }
    }

    @Override
    public Object get(int index) {
        return arr[index];
    }

    @Override
    public int getSize() {
        return size;
    }

    @Override
    public Iterator iterator() {
        return new ConcreteIterator(this);
    }
}
Iterator:迭代器角色
public interface Iterator {
    boolean hasNext();
    Object next();
}
ConcreteIterator 具体的迭代器
public class ConcreteIterator implements Iterator {
    //迭代器是为了对容器角色遍历,具体的迭代器需要关联容器角色
    private Aggregate aggregate;
    private int index;

    public ConcreteIterator(Aggregate aggregate) {
        this.aggregate = aggregate;
    }

    @Override
    public boolean hasNext() {
        if(index >= aggregate.getSize()){
            return false;
        }
        return true;
    }

    @Override
    public Object next() {
        Object object  = aggregate.get(index);
        index++;
        return object;
    }
}
Test 测试类
@Slf4j
public class Test {
    public static void main(String[] args) {
        Aggregate aggregate = new ConcreteAggregate();
        aggregate.add("宋江");
        aggregate.add("武松");

        Iterator iterator = aggregate.iterator();
        log.info("aggregate size {}", aggregate.getSize());
        //无须暴露内部表示
        while (iterator.hasNext()){
            log.info("{}", iterator.next());
        }
    }
}
输出结果

优点

应用场景

总结

举报

相关推荐

0 条评论