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前言

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一、迭代器模式基本介绍

二、迭代器模式应用实例

完整代码

Department 系

package tanchishell.SJMS.iterator;


//系
public class Department {

    private String name;
    private String desc;

    public Department(String name, String desc) {
        super();
        this.name = name;
        this.desc = desc;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getDesc() {
        return desc;
    }

    public void setDesc(String desc) {
        this.desc = desc;
    }
}

ComputerCollegeIterator 计算机学院迭代器

package tanchishell.SJMS.iterator;

import java.util.Iterator;

public class ComputerCollegeIterator implements Iterator {
    //这里我们需要 Department 是以怎样的方式存放=>数组
    Department[] departments;
    int position = 0; //遍历的位置

    public ComputerCollegeIterator(Department[] departments) {
        this.departments = departments;
    }

    //判断是否还有下一个元素
    @Override
    public boolean hasNext() {

        if (position >= departments.length || departments[position] == null) {
            return false;
        } else {
            return true;
        }
    }

    @Override
    public Object next() {

        Department department = departments[position];
        position += 1;
        return department;
    }

    //删除的方法，默认空实现
    public void remove() {
    }
}

InfoColleageIterator 信息工程学院迭代器

package tanchishell.SJMS.iterator;

import java.util.Iterator;
import java.util.List;

public class InfoColleageIterator implements Iterator {

    List<Department> departmentList; // 信息工程学院是以 List 方式存放系
    int index = -1;//索引

    public InfoColleageIterator(List<Department> departmentList) {
        this.departmentList = departmentList;
    }

    //判断 list 中还有没有下一个元素
    @Override
    public boolean hasNext() {
        if (index >= departmentList.size() - 1) {
            return false;
        } else {
            index += 1;
            return true;
        }
    }

    @Override
    public Object next() {

        return departmentList.get(index);
    }

    //空实现 remove
    public void remove() {
    }
}

College 学院接口

package tanchishell.SJMS.iterator;

import java.util.Iterator;

//学院
public interface College {

    public String getName();

    //增加系的方法
    public void addDepartment(String name, String desc);

    //返回一个迭代器,遍历
    public Iterator createIterator();
}

ComputerCollege 计算机学院

package tanchishell.SJMS.iterator;

import java.util.Iterator;

public class ComputerCollege implements College {

    Department[] departments;
    int numOfDepartment = 0;// 保存当前数组的对象个数

    public ComputerCollege() {
        departments = new Department[5];
        addDepartment("Java 专业", " Java 专业 ");
        addDepartment("PHP 专业", " PHP 专业 ");
        addDepartment("大数据专业", " 大数据专业 ");
    }

    @Override
    public String getName() {

        return "计算机学院";
    }

    @Override
    public void addDepartment(String name, String desc) {

        Department department = new Department(name, desc);
        departments[numOfDepartment] = department;
        numOfDepartment += 1;
    }

    @Override
    public Iterator createIterator() {

        return new ComputerCollegeIterator(departments);
    }
}

InfoCollege 信息工程学院

package tanchishell.SJMS.iterator;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

public class InfoCollege implements College {

    List<Department> departmentList;

    public InfoCollege() {
        departmentList = new ArrayList<Department>();
        addDepartment("信息安全专业", " 信息安全专业 ");
        addDepartment("网络安全专业", " 网络安全专业 ");
        addDepartment("服务器安全专业", " 服务器安全专业 ");
    }


    @Override
    public String getName() {

        return "信息工程学院";
    }

    @Override
    public void addDepartment(String name, String desc) {

        Department department = new Department(name, desc);
        departmentList.add(department);
    }

    @Override
    public Iterator createIterator() {

        return new InfoColleageIterator(departmentList);
    }
}

OutPutImpl 操作迭代器

package tanchishell.SJMS.iterator;

import java.util.Iterator;
import java.util.List;

public class OutPutImpl {


    //学院集合
    List<College> collegeList;

    public OutPutImpl(List<College> collegeList) {
        this.collegeList = collegeList;
    }

    //遍历所有学院,然后调用 printDepartment 输出各个学院的系
    public void printCollege() {
        //从 collegeList 取出所有学院, Java 中的 List 已经实现 Iterator
        Iterator<College> iterator = collegeList.iterator();
        while (iterator.hasNext()) {
            //取出一个学院
            College college = iterator.next();
            System.out.println("=== " + college.getName() + "=====");
            printDepartment(college.createIterator()); //得到对应迭代器
        }
    }

    //输出 学院输出 系
    public void printDepartment(Iterator iterator) {
        while (iterator.hasNext()) {
            Department d = (Department) iterator.next();
            System.out.println(d.getName());
        }
    }
}

Clint 测试

package tanchishell.SJMS.iterator;

import java.util.ArrayList;
import java.util.List;

public class Client {

    public static void main(String[] args) {
        //创建学院
        List<College> collegeList = new ArrayList<College>();
        ComputerCollege computerCollege = new ComputerCollege();
        InfoCollege infoCollege = new InfoCollege();
        collegeList.add(computerCollege);
        collegeList.add(infoCollege);
        OutPutImpl outPutImpl = new OutPutImpl(collegeList);
        outPutImpl.printCollege();
    }
}


输出

=== 计算机学院=====
Java 专业
PHP 专业
大数据专业
=== 信息工程学院=====
信息安全专业
网络安全专业
服务器安全专业

三、迭代器模式在 JDK-ArrayList 集合应用的源码分析

四、迭代器模式的注意事项和细节