Java集合-使用Iterator迭代器遍历List_Set_Map和容器遍历方法汇总_iterator可以用来遍历set和list集合

使用Iterator迭代器遍历

1. 使用Iterator迭代器遍历List、Set、Map

import java.util.*;

public class IteratorTest {
    public static void main(String[] args) {
        iteratorList();
        iteratorSet();
        iteratorMap();
    }

    /**
     * 通过迭代器Iterator遍历list
     */
    public static void iteratorList(){
        List<String> list = new ArrayList<String>();
        list.add("a");
        list.add("b");
        list.add("c");
        list.add("d");
        list.add("e");

        for(Iterator iterator = list.iterator();iterator.hasNext(); ){
            String s = (String) iterator.next();
            System.out.println(s);
        }
    }

    /**
     * 通过迭代器Iterator遍历Set
     */
    public static void iteratorSet(){
        Set<String> set = new HashSet<>();
        set.add("aa");
        set.add("bb");
        set.add("cc");
        set.add("dd");
        set.add("ee");

        for(Iterator iterator = set.iterator();iterator.hasNext(); ){
            String s = (String) iterator.next();
            System.out.println(s);
        }
    }
	/**
     * 通过迭代器Iterator遍历Map
     */
    public static void iteratorMap(){
        Map<Integer, String> map = new HashMap<>();
        map.put(1001,"Ano");
        map.put(1002,"Jack");
        map.put(1003,"Charlie");
        Set<Integer> keys = map.keySet();

        for(Iterator iterator = keys.iterator();iterator.hasNext();){
            Integer integer = (Integer) iterator.next();
            String value = map.get(integer);
            System.out.println(integer +" =" +value);
        }
    }
}
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2. 遍历容器方法汇总

import java.util.List;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
import java.util.Map.Entry;

public class TestThroughCollection {
    /**
     * 遍历list
     * @param list
     * @param <E>
     */
    public static <E> void throughList(List<E> list){
        //1.普通for循环
        for(int i =0; i < list.size(); i++){
            E e = list.get(i);
            System.out.println(e);
        }

        //2.增强for循环
        for(E e : list){
            System.out.println(e);
        }

        //3.使用Iterator迭代器(1)
        for(Iterator iterator = list.iterator(); iterator.hasNext();){
            E e = (E)iterator.next();
            System.out.println(e);
        }

        //4.使用Iterator迭代器(2)
        Iterator it = list.iterator();
        while(it.hasNext()){
            E e = (E)it.next();
            System.out.println(e);
        }
    }

    /**
     * 遍历Set
     * @param set
     * @param <E>
     */
    public static <E> void throughSet(Set<E> set){
        //1.增强for循环
        for(E e : set){
            System.out.println(e);
        }

        //2.Iterator迭代器
        for(Iterator iterator = set.iterator(); iterator.hasNext();){
            E e = (E)iterator.next();
            System.out.println(e);
        }

    }

    /**
     * 遍历Map
     * @param map
     * @param <K>
     * @param <V>
     */
    public static <K, V> void throughMap(Map<K, V> map){
        //1.根据Key获取value
        Set<K> set = map.keySet();
        for(Iterator it = set.iterator(); it.hasNext();){
            K key = (K)it.next();
            V value = map.get(key);
        }

        //2.使用entrySet
        Set<Entry<K,V>> ss = map.entrySet();
        //2.1
        for(Entry<K,V> entry : ss){
            System.out.println(entry);
        }
        //2.2
        /*
        for(Iterator it = ss.iterator(); it.hasNext();){
            Entry<K, V> entry = (Entry<K, V>) it.next();
            System.out.println(entry);
            System.out.println(entry.getKey() + "=" + entry.getValue());
        }
         */
    }
}
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