{"id":1123,"date":"2023-03-16T21:23:41","date_gmt":"2023-03-16T13:23:41","guid":{"rendered":"https:\/\/www.appblog.cn\/?p=1123"},"modified":"2023-04-29T10:16:35","modified_gmt":"2023-04-29T02:16:35","slug":"design-pattern-iterator-pattern","status":"publish","type":"post","link":"https:\/\/www.appblog.cn\/index.php\/2023\/03\/16\/design-pattern-iterator-pattern\/","title":{"rendered":"\u8bbe\u8ba1\u6a21\u5f0f\uff0814\uff09\u8fed\u4ee3\u5668\u6a21\u5f0f"},"content":{"rendered":"

\u8fed\u4ee3\u5668\u6a21\u5f0f\uff0c\u53c8\u53eb\u505a\u6e38\u6807\u6a21\u5f0f\uff0c\u662f\u884c\u4e3a\u578b\u8bbe\u8ba1\u6a21\u5f0f\u4e4b\u4e00\u3002\u6211\u4eec\u77e5\u9053\u5bf9\u5bb9\u5668\u5bf9\u8c61\u7684\u8bbf\u95ee\u5fc5\u7136\u4f1a\u6d89\u53ca\u904d\u5386\u7b97\u6cd5\uff0c\u6211\u4eec\u53ef\u4ee5\u5c06\u904d\u5386\u7684\u65b9\u6cd5\u5c01\u88c5\u5728\u5bb9\u5668\u4e2d\uff0c\u6216\u8005\u4e0d\u63d0\u4f9b\u904d\u5386\u65b9\u6cd5\uff0c\u8ba9\u4f7f\u7528\u5bb9\u5668\u7684\u4eba\u81ea\u5df1\u53bb\u5b9e\u73b0\u53bb\u5427\u3002\u8fd9\u4e24\u79cd\u60c5\u51b5\u597d\u50cf\u90fd\u80fd\u591f\u89e3\u51b3\u95ee\u9898\u3002<\/p>\n

<\/p>\n

\u7136\u800c\u5728\u524d\u4e00\u79cd\u60c5\u51b5\uff0c\u5bb9\u5668\u627f\u53d7\u4e86\u8fc7\u591a\u7684\u529f\u80fd\uff0c\u5b83\u4e0d\u4ec5\u8981\u8d1f\u8d23\u81ea\u5df1\u201c\u5bb9\u5668\u201d\u5185\u7684\u5143\u7d20\u7ef4\u62a4\uff08\u6dfb\u52a0\u3001\u5220\u9664\u7b49\u7b49\uff09\uff0c\u800c\u4e14\u8fd8\u8981\u63d0\u4f9b\u904d\u5386\u81ea\u8eab\u7684\u63a5\u53e3\uff1b\u800c\u4e14\u7531\u4e8e\u904d\u5386\u72b6\u6001\u4fdd\u5b58\u7684\u95ee\u9898\uff0c\u4e0d\u80fd\u5bf9\u540c\u4e00\u4e2a\u5bb9\u5668\u5bf9\u8c61\u540c\u65f6\u8fdb\u884c\u591a\u4e2a\u904d\u5386\u3002\u7b2c\u4e8c\u79cd\u65b9\u5f0f\u5012\u662f\u7701\u4e8b\uff0c\u5374\u53c8\u5c06\u5bb9\u5668\u7684\u5185\u90e8\u7ec6\u8282\u66b4\u9732\u65e0\u9057\u3002<\/p>\n

\u6b63\u56e0\u4e8e\u6b64\uff0c\u8fed\u4ee3\u5668\u6a21\u5f0f\u5e94\u8fd0\u800c\u751f\uff0c\u5728\u5ba2\u6237\u8bbf\u95ee\u7c7b\u4e0e\u5bb9\u5668\u4f53\u4e4b\u95f4\u63d2\u5165\u4e00\u4e2a\u7b2c\u4e09\u8005\u2013\u8fed\u4ee3\u5668\uff0c\u5f88\u597d\u7684\u89e3\u51b3\u4e86\u4e0a\u8ff0\u5f0a\u7aef\u3002<\/p>\n

\u5b9a\u4e49<\/h2>\n

\u63d0\u4f9b\u4e00\u79cd\u65b9\u6cd5\u987a\u5e8f\u8bbf\u95ee\u4e00\u4e2a\u5bb9\u5668\u5bf9\u8c61\u4e2d\u7684\u5404\u4e2a\u5143\u7d20\uff0c\u800c\u53c8\u4e0d\u9700\u8981\u66b4\u9732\u8be5\u5bf9\u8c61\u7684\u5185\u90e8\u8868\u793a\u3002<\/p>\n

\u4f7f\u7528\u573a\u666f<\/h2>\n

\u904d\u5386\u4e00\u4e2a\u5bb9\u5668\u5bf9\u8c61\u65f6\u3002<\/p>\n

\u7b80\u5355\u5b9e\u73b0<\/h2>\n

\u7528\u4e66\u4e2d\u7684\u4f8b\u5b50\uff1a\u5c0f\u6c11\u548c\u5c0f\u8f89\u5206\u522b\u5728\u516c\u53f8\u4e24\u4e2a\u4e8b\u4e1a\u90e8\uff0c\u67d0\u5929\u8001\u677f\u5b89\u6392\u4efb\u52a1\u8ba9\u4ed6\u4eec\u4fe9\u7edf\u8ba1\u4e00\u4e0b\u5404\u81ea\u90e8\u95e8\u7684\u5458\u5de5\u6570\u636e\u3002<\/p>\n

\u5458\u5de5\u5b9e\u4f53\u7c7b\uff1a<\/p>\n

public class Employee {\n\n    private String name;\/\/ \u59d3\u540d\n    private int age;\/\/ \u5e74\u9f84\n    private String sex;\/\/ \u6027\u522b\n    private String position;\/\/ \u804c\u4f4d\n\n    public Employee(String name, int age, String sex, String position) {\n        super();\n        this.name = name;\n        this.age = age;\n        this.sex = sex;\n        this.position = position;\n    }\n\n    \/\/ \u7b80\u5316\u4ee3\u7801\uff0c\u7701\u7565setter\u548cgetter\u65b9\u6cd5\n\n    @Override\n    public String toString() {\n        return "Employee{" + "name='" + name + '\\'' + ", age=" + age + ", sex="\n                + sex + ", position='" + position + '\\'' + "}";\n    }\n}<\/code><\/pre>\n
\u5c0f\u8f89\u90e8\u95e8\uff1a<\/p>\n
public class CompanyHui {\n\nprivate Employee[] array = new Employee[3];\n\n    public CompanyHui(){\n        array[0] = new Employee("\u8f89\u54e5", 28, "\u7537", "\u7a0b\u5e8f\u733f");\n        array[1] = new Employee("\u5c0f\u7ea2", 23, "\u7537", "\u7a0b\u5e8f\u733f");\n        array[2] = new Employee("\u5c0f\u8f89", 25, "\u7537", "\u7a0b\u5e8f\u733f");\n    }\n\n    public Employee[] getEmployees(){\n        return array;\n    }\n}<\/code><\/pre>\n
\u5c0f\u6c11\u90e8\u95e8\uff1a<\/p>\n
public class CompanyMin {\n\n    private List<Employee> list = new ArrayList<>();\n\n    public CompanyMin(){\n        list.add(new Employee("\u5c0f\u6c11", 26, "\u7537", "\u7a0b\u5e8f\u733f"));\n        list.add(new Employee("\u5c0f\u82b8", 22, "\u5973", "\u6d4b\u8bd5"));\n        list.add(new Employee("\u5c0f\u65b9", 18, "\u5973", "\u6d4b\u8bd5"));\n        list.add(new Employee("\u53ef\u513f", 21, "\u5973", "\u8bbe\u8ba1"));\n        list.add(new Employee("\u6717\u60c5", 19, "\u5973", "\u8bbe\u8ba1")); \/\/\u5410\u69fd\u4e00\u4e0b\uff0c\u4e3a\u4ec0\u4e48\u5c31\u5c0f\u6c11\u4e00\u4e2a\u7537\u7684\uff0c\u5c0f\u8f89\u90e8\u95e8\u5168\u7537\u7684\u3002\n    }\n\n    public List<Employee> getEmployees(){\n        return list;\n    }\n}<\/code><\/pre>\n
Boss\u67e5\u770b\uff1a<\/p>\n
public class Boss {\n    public static void main(String[] args) {\n        CompanyHui hui = new CompanyHui();\n        Employee[] huiList = hui.getEmployees();\n        for(int i = 0; i < huiList.length; i++){\n            System.out.println(huiList[i]);\n        }\n\n        CompanyMin min = new CompanyMin();\n        List minList = min.getEmployees();\n        for(int i = 0; i < minList.size(); i++){\n            System.out.println(minList.get(i).toString());\n        }\n    }\n}<\/code><\/pre>\n
\u7ed3\u679c\uff1a<\/p>\n
Employee{name='\u8f89\u54e5', age=28, sex=\u7537, position='\u7a0b\u5e8f\u733f'}\nEmployee{name='\u5c0f\u7ea2', age=23, sex=\u7537, position='\u7a0b\u5e8f\u733f'}\nEmployee{name='\u5c0f\u8f89', age=25, sex=\u7537, position='\u7a0b\u5e8f\u733f'}\nEmployee{name='\u5c0f\u6c11', age=26, sex=\u7537, position='\u7a0b\u5e8f\u733f'}\nEmployee{name='\u5c0f\u82b8', age=22, sex=\u5973, position='\u6d4b\u8bd5'}\nEmployee{name='\u5c0f\u65b9', age=18, sex=\u5973, position='\u6d4b\u8bd5'}\nEmployee{name='\u53ef\u513f', age=21, sex=\u5973, position='\u8bbe\u8ba1'}\nEmployee{name='\u6717\u60c5', age=19, sex=\u5973, position='\u8bbe\u8ba1'}<\/code><\/pre>\n
\u8fd9\u6837\u770b\u4f3c\u4e5f\u6ca1\u6709\u95ee\u9898\uff0c\u4f46\u662f\u5982\u679c\u6709\u591a\u4e2a\u90e8\u95e8\uff0c\u6bcf\u4e2a\u90e8\u95e8\u6709\u5404\u81ea\u7684\u5b9e\u73b0\uff0c\u90a3\u4e48\u6211\u4eec\u5c31\u8981\u5728Boss\u7c7b\u4e2d\u589e\u52a0\u4e00\u904d\u904d\u5386\u903b\u8f91\uff0c\u8fd9\u6837Boss\u7c7b\u7684\u529f\u80fd\u4f1a\u8d8a\u6765\u8d8a\u591a\uff0c\u540c\u65f6\u66b4\u9732\u4e86\u5185\u90e8\u7ec6\u8282\u3002\u90a3\u4e48\u6211\u4eec\u9700\u8981\u5b9a\u4e49\u4e00\u4e2a\u8fed\u4ee3\u5668\u63a5\u53e3\uff1a<\/p>\n
public interface Iterator {\n\n    \/**\n     * \u662f\u5426\u8fd8\u6709\u4e0b\u4e00\u4e2a\u5143\u7d20 \n     * \n     * @return true\u8868\u793a\u6709\uff0cfalse\u8868\u793a\u6ca1\u6709\n     *\/\n    boolean hasNext();\n\n    \/**\n     * \u8fd4\u56de\u5f53\u524d\u5143\u7d20\uff0c\u5e76\u5c06\u4f4d\u7f6e\u79fb\u81f3\u4e0b\u4e00\u4f4d\n     *\/\n    Object next();\n}<\/code><\/pre>\n
\u5c0f\u6c11\u7684\u8fed\u4ee3\u5668\uff1a<\/p>\n
public class MinIterator implements Iterator {\n\n    private List<Employee> list;\n    private int position;\n\n    public MinIterator(List<Employee> list) {\n        this.list = list;\n    }\n\n    @Override\n    public boolean hasNext() {\n        return !(position > list.size() - 1 || list.get(position) == null);\n    }\n\n    @Override\n    public Object next() {\n        Employee e = list.get(position);\n        position++;\n        return e;\n    }\n\n}<\/code><\/pre>\n
\u5c0f\u8f89\u7684\u8fed\u4ee3\u5668\uff1a<\/p>\n
public class HuiIterator implements Iterator{\n\n    private Employee[] array;\n    private int position;\n\n    public HuiIterator(Employee[] array){\n        this.array = array;\n    }\n\n    @Override\n    public boolean hasNext() {\n        return !(position > array.length - 1 || array[position] == null);\n    }\n\n    @Override\n    public Object next() {\n        Employee e = array[position];\n        position++;\n        return e;\n    }\n\n}<\/code><\/pre>\n
\u5b9a\u4e49\u5bb9\u5668\u7c7b\u7684\u63a5\u53e3<\/p>\n
public interface Company {\n\n    \/**\n     * \u8fd4\u56de\u4e00\u4e2a\u8fed\u4ee3\u5668\u5bf9\u8c61\n     * \n     * @return \u8fed\u4ee3\u5668\u5bf9\u8c61\n     *\/\n    Iterator iterator();\n\n}<\/code><\/pre>\n
\u4fee\u6539\u4e00\u4e0b\u4e4b\u524d\u7684\u4e24\u4e2a\u5bb9\u5668\u7c7b\uff1a<\/p>\n
public class CompanyHui implements Company{\n\n    private Employee[] array = new Employee[3];\n\n    public CompanyHui(){\n        array[0] = new Employee("\u8f89\u54e5", 28, "\u7537", "\u7a0b\u5e8f\u733f");\n        array[1] = new Employee("\u5c0f\u7ea2", 23, "\u7537", "\u7a0b\u5e8f\u733f");\n        array[2] = new Employee("\u5c0f\u8f89", 25, "\u7537", "\u7a0b\u5e8f\u733f");\n    }\n\n    public Employee[] getEmployees(){\n        return array;\n    }\n\n    @Override\n    public Iterator iterator() {\n        return new HuiIterator(array);\n    }\n}<\/code><\/pre>\n
public class CompanyMin implements Company{\n\n    private List<Employee> list = new ArrayList<>();\n\n    public CompanyMin(){\n        list.add(new Employee("\u5c0f\u6c11", 26, "\u7537", "\u7a0b\u5e8f\u733f"));\n        list.add(new Employee("\u5c0f\u82b8", 22, "\u5973", "\u6d4b\u8bd5"));\n        list.add(new Employee("\u5c0f\u65b9", 18, "\u5973", "\u6d4b\u8bd5"));\n        list.add(new Employee("\u53ef\u513f", 21, "\u5973", "\u8bbe\u8ba1"));\n        list.add(new Employee("\u6717\u60c5", 19, "\u5973", "\u8bbe\u8ba1"));\n    }\n\n    public List<Employee> getEmployees(){\n        return list;\n    }\n\n    @Override\n    public Iterator iterator() {\n        return new MinIterator(list);\n    }\n}<\/code><\/pre>\n
Boss\u67e5\u770b\uff1a<\/p>\n
public class Boss {\n    public static void main(String[] args) {\n        CompanyHui hui = new CompanyHui();\n        check(hui.iterator());\n\n        CompanyMin min = new CompanyMin();\n        check(min.iterator());\n    }\n\n    private static void check(Iterator iterator){\n        while (iterator.hasNext()) {\n            System.out.println(iterator.next().toString());\n        }\n    }\n}<\/code><\/pre>\n
\u7ed3\u679c\u4e0d\u53d8\uff0c\u5c31\u4e0d\u91cd\u590d\u5199\u4e86\u3002<\/p>\n
Android\u6e90\u7801\u4e2d\u7684\u6a21\u5f0f\u5b9e\u73b0<\/h2>\n
    \n
  • Cursor<\/li>\n<\/ul>\n
    \u5f53\u6211\u4eec\u4f7f\u7528SQLiteDatabase<\/code>\u7684query<\/code>\u65b9\u6cd5\u67e5\u8be2\u6570\u636e\u5e93\u65f6\uff0c\u4f1a\u8fd4\u56de\u4e00\u4e2aCursor<\/code>\u6e38\u6807\u5bf9\u8c61\uff0c\u8be5\u6e38\u6807\u7684\u5b9e\u8d28\u5c31\u662f\u4e00\u4e2a\u5177\u4f53\u7684\u8fed\u4ee3\u5668\uff0c\u6211\u4eec\u53ef\u4ee5\u4f7f\u7528\u5b83\u6765\u904d\u5386\u6570\u636e\u5e93\u67e5\u8be2\u6240\u5f97\u7684\u7ed3\u679c\u96c6\u3002<\/p>\n
    \u603b\u7ed3<\/h2>\n
    \u8fed\u4ee3\u5668\u6a21\u5f0f\u53d1\u5c55\u81f3\u4eca\uff0c\u51e0\u4e4e\u6240\u6709\u7684\u9ad8\u7ea7\u8bed\u8a00\u90fd\u6709\u76f8\u5e94\u7684\u5185\u7f6e\u5b9e\u73b0\uff0c\u5bf9\u4e8e\u5f00\u53d1\u8005\u800c\u8a00\uff0c\u5df2\u7ecf\u6781\u5c11\u4f1a\u81ea\u5df1\u53bb\u5b9e\u73b0\u8fed\u4ee3\u5668\u4e86\uff0c\u6240\u4ee5\u672c\u7ae0\u5185\u5bb9\u66f4\u591a\u7684\u662f\u4e86\u89e3\u800c\u975e\u5e94\u7528\u3002<\/p>\n
      \n
    • \u4f18\u70b9<\/li>\n<\/ul>\n
      \uff081\uff09\u7b26\u5408\u9762\u5411\u5bf9\u8c61\u8bbe\u8ba1\u539f\u5219\u4e2d\u7684\u5355\u4e00\u804c\u8d23\u539f\u5219
      \n\uff082\uff09\u652f\u6301\u5bf9\u5bb9\u5668\u5bf9\u8c61\u7684\u591a\u79cd\u904d\u5386\u3002\u5f31\u5316\u4e86\u5bb9\u5668\u7c7b\u4e0e\u904d\u5386\u7b97\u6cd5\u4e4b\u95f4\u7684\u5173\u7cfb<\/p>\n
        \n
      • \u7f3a\u70b9<\/li>\n<\/ul>\n
        \uff081\uff09\u7c7b\u6587\u4ef6\u7684\u589e\u52a0
        \n\uff083\uff09\u4f1a\u51fa\u73b0ConcurrentModificationException<\/code>\u5f02\u5e38
        \n\uff082\uff09\u904d\u5386\u8fc7\u7a0b\u662f\u4e00\u4e2a\u5355\u5411\u4e14\u4e0d\u53ef\u9006\u7684\u904d\u5386<\/p>\n","protected":false},"excerpt":{"rendered":"
        \u8fed\u4ee3\u5668\u6a21\u5f0f\uff0c\u53c8\u53eb\u505a\u6e38\u6807\u6a21\u5f0f\uff0c\u662f\u884c\u4e3a\u578b\u8bbe\u8ba1\u6a21\u5f0f\u4e4b\u4e00\u3002\u6211\u4eec\u77e5\u9053\u5bf9\u5bb9\u5668\u5bf9\u8c61\u7684\u8bbf\u95ee\u5fc5\u7136\u4f1a\u6d89\u53ca\u904d\u5386\u7b97\u6cd5\uff0c\u6211\u4eec\u53ef\u4ee5\u5c06\u904d\u5386\u7684 […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[303],"tags":[],"class_list":["post-1123","post","type-post","status-publish","format-standard","hentry","category-design-pattern"],"_links":{"self":[{"href":"https:\/\/www.appblog.cn\/index.php\/wp-json\/wp\/v2\/posts\/1123","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.appblog.cn\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.appblog.cn\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.appblog.cn\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.appblog.cn\/index.php\/wp-json\/wp\/v2\/comments?post=1123"}],"version-history":[{"count":0,"href":"https:\/\/www.appblog.cn\/index.php\/wp-json\/wp\/v2\/posts\/1123\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.appblog.cn\/index.php\/wp-json\/wp\/v2\/media?parent=1123"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.appblog.cn\/index.php\/wp-json\/wp\/v2\/categories?post=1123"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.appblog.cn\/index.php\/wp-json\/wp\/v2\/tags?post=1123"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}