Java基础——Iterator和Iterable

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文章代码来自：来源

含义

• Iterable接口：实现了Iterable接口的类表明了属于该类的对象能够使用for each进行迭代
• Iterator接口：用以实现迭代机制的接口

内部实现

• Iterable接口

public interface Iterable
{
    Iterator<E> iterator();
}

• Iterator接口

public interface Iterator
{
    E next();
    boolean hasNext();
    void remove();
}

举例说明

• 以下总共有两个类，一个Student，一个Students，通过Students实现了Iterator和Iterable接口

/*
    Student 类
*/
public class Student{
    private String name;
    private String Id;

    public Student(String name,String Id){
        this.name = name;
        this.Id = Id;
    }

    public String getName(){
        return name;
    }

    public String getId(){
        return Id;
    } 

    @Override
    public String toString(){
        return "[" + this.getClass() + " : " + this.name + " , " + this.Id + "]"; 
    }
}
/*
    Students 类
*/
public class Students implements Iterable<Student>
{
    private Student[] records;
    public Students(int length){
        records = new Student[length];
        for(int index = 0; index < length; index++){
            records[index] = new Student("学生" + index , index);
        } 
    }

    public Iterator<Student> iterator(){
        return new StudentsIterator();
    }

    private class StudentsIterator implements Iterator<Student>{
        private int index = 0;
        public Student next()
        {
            return records[index++];
        }

        public boolean hasNext()
        {
            return (index < records.length);
        }

        public void remove()
        {
            //抛出不支持操作异常
            throw new UnsupportedOperationException();
        }
    }
}

／*
    main 函数
*／

public class Demo{
    public static void main(String[] args)
    {
        Students students = new Students(5);

        for(Student student : students)
        {
            System.out.println(student);
        }
    }
}

过程中产生的疑问

• 数组类型的变量只有length属性，那要如何获得该变量的元素个数，只能通过设置一个count计数器吗？相关链接
• 数组也是一个对象，例如

...
Object b = new int[5];
...