迭代器就是迭代器模式_迭代器模式和迭代器一样吗-优快云博客

本文链接：https://blog.youkuaiyun.com/qq_42520962/article/details/107974228

本文探讨了迭代器模式的概念，通过Java代码示例详细解释了如何实现Iterable和Iterator接口来遍历集合。对比分析了直接实现Iterator与通过Iterable返回Iterator的区别，强调了其在不同迭代需求场景下的灵活性。

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看书了半天，个人浅显的认为迭代器模式就是实现了一个迭代器。

class MyIter{
    private List<Object> ob = new ArrayList<>();
    private int i = 0;
    public boolean hasnext(){
        if (i < ob.size()){
            return true;
        }else{
            return false;
        }
    }
    public Object get(){
        if (hasnext()){
            return ob.get(i++);
        }else{
            return null;
        }
    }
}

但是Java里面有个Iterable和Iterator的接口

Iterator使用例子：

源码：

package java.util;

import java.util.function.Consumer;

public interface Iterator<E> {

    boolean hasNext();

    E next();

    default void remove() {
        throw new UnsupportedOperationException("remove");
    }

    default void forEachRemaining(Consumer<? super E> action) {
        Objects.requireNonNull(action);
        while (hasNext())
            action.accept(next());
    }
}

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

public class App {
    public static void main(final String[] args) throws Exception {
        List<Object> ob = new ArrayList<>();
        ob.add("1");
        ob.add("2");
        ob.add("3");
        ob.add("4");
        Iterator myiterator = new MyIterator(ob);
        while (myiterator.hasNext()){
            System.out.println(myiterator.next());
        }
    }
}


class MyIterator implements Iterator {
    private List<Object> ob = new ArrayList<>();
    private int i = 0;
    
    MyIterator(List<Object> ob){
        this.ob = ob;
    }    

    @Override
    public boolean hasNext() {
        if (i < ob.size()){
            return true;
        }else{
            return false;
        }
    }

    @Override
    public Object next() {
        if (hasNext()){
            return ob.get(i++);
        }else{
            return null;
        }
    }
}

/*
结果
1
2
3
4
*/

Iterable使用例子：

源码：

import java.util.Iterator;
import java.util.Objects;
import java.util.Spliterator;
import java.util.Spliterators;
import java.util.function.Consumer;


public interface Iterable<T> {
    Iterator<T> iterator();

    default void forEach(Consumer<? super T> action) {
        Objects.requireNonNull(action);
        for (T t : this) {
            action.accept(t);
        }
    }

    default Spliterator<T> spliterator() {
        return Spliterators.spliteratorUnknownSize(iterator(), 0);
    }
}

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

public class App {
    public static void main(final String[] args) throws Exception {
        List<Object> ob = new ArrayList<>();
        ob.add("1");
        ob.add("2");
        ob.add("3");
        ob.add("4");
        Iterable myiterable = new MyIterable(ob);
        Iterator myiterator = myiterable.iterator();
        while (myiterator.hasNext()){
            System.out.println(myiterator.next());
        }
    }
}

class MyIterable implements Iterable {
    private List<Object> ob = new ArrayList<>();
    private int i = 0;

    MyIterable(List<Object> ob){
        this.ob = ob;
    }

    @Override
    public Iterator iterator() {
        // TODO Auto-generated method stub
        return new MyIterator();
    }
    private class MyIterator implements Iterator{

        @Override
        public boolean hasNext() {
            if (i < ob.size()){
                return true;
            }else{
                return false;
            }
        }

        @Override
        public Object next() {
            if (hasNext()){
                return ob.get(i++);
            }else{
                return null;
            }
        }

    } 
}

/*
结果
1
2
3
4
*/