Arraylist循环方法

Arraylist循环学习

普通for循环

public class arraylist_stu {
    public static void main(String[] args) {
        ArrayList<String> a = new ArrayList<>(
                Collections.nCopies(22,"zz"));
        for(int i = 0;i<a.size();i++){
            System.out.println(a.get(i));
        }
    }
}

• 相关函数

  • get(int index)

    获取下标为index的值是多少

  • Collection.nCopices(int count,hh)

    将数组在0~count处全部放置相同的值hh;

for-each

public class arraylist_stu {
    public static void main(String[] args) {
        ArrayList<String> a = new ArrayList<>(
                Collections.nCopies(22,"zz"));
        for(String k:a){
            System.out.println(k);
        }
    }
}

while

public class arraylist_stu {
    public static void main(String[] args) {
        ArrayList<String> a = new ArrayList<>(
                Collections.nCopies(22,"zz"));
        int d = 0;
        while(a.size() > d){

            System.out.println(a.get(d++ ));
        }
    }
}

迭代器Iterator

public class arraylist_stu {
    public static void main(String[] args) {
        ArrayList<String> a = new ArrayList<>(
                Collections.nCopies(22,"zz"));
        int d = 0;
        Iterator f =a.iterator();
        while(f.hasNext()){

            System.out.println(f.next());
        }
    }
}

• iterator是迭代器用来遍历数组

使用数组的方法创建迭代器

然后使用hasNext判断是否读取完毕

next获取下一个元素

---

枚举enumeration迭代arraylist

public class arraylist_stu {
    public static void main(String[] args) {
        ArrayList<String> a = new ArrayList<>(
                Collections.nCopies(22,"zz"));

        Enumeration<String> d = Collections.enumeration(a);
        while(d.hasMoreElements()){

            System.out.println(d.nextElement());
        }
    }
}