02 迭代器

1 Iterator 的基本使用

迭代器统一了对集合的访问方式。注意迭代器在集合层次中的位置。

package com.hcong.collections;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Iterator;

/**
 * @Classname SimpleIteration
 * @Date 2023/4/4 16:16
 * @Created by HCong
 */
public class SimpleIteration {
    public static void main(String[] args) {
        // 1.迭代器遍历
        Collection<Integer> collection = new ArrayList<>(Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10));
        Iterator<Integer> it = collection.iterator();
        while (it.hasNext()) {
            Integer next = it.next();
            System.out.print(next + " ");
        }
        System.out.println();

        // 2.for-in
        for (Integer i : collection) {
            System.out.print(i + " ");
        }
        System.out.println();

        // 3.迭代器删除元素
        it = collection.iterator();
        for (int i = 0; i < 5; i++) {
            it.next();
            it.remove();
        }
        System.out.println(collection);
    }
}

1 2 3 4 5 6 7 8 9 10 
1 2 3 4 5 6 7 8 9 10 
[6, 7, 8, 9, 10]

2 ListIterator 的基本使用

package com.hcong.collections;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.ListIterator;

/**
 * @Classname ListIteration
 * @Date 2023/4/4 16:35
 * @Created by HCong
 */
public class ListIteration {
    public static void main(String[] args) {
        List<String> list = new ArrayList<>(Arrays.asList("A", "B", "C", "D", "E", "F", "G"));
        ListIterator<String> lit = list.listIterator();
        while (lit.hasNext()) {
            String next = lit.next();
            System.out.println(next + " " + lit.nextIndex() + " " + lit.previousIndex() + " ");
        }
        System.out.println();
    }
}

A 1 0 
B 2 1 
C 3 2 
D 4 3 
E 5 4 
F 6 5 
G 7 6