Java分页需求

近期在实现项目接口时，经常需要分页功能。有时返回“String”,有时是“Object”格式的分页List。针对这种情况，本人用java实现对List分页。

第一版

package org.sun.java;

import java.util.ArrayList;

import java.util.List;

/**

 *

 * @author Administrator

 * @date 2016年7月16日

 */

public class SubListOperation {

    final static int COUNT = 18;

    public List<String> init(int size) {

        List<String> lists = new ArrayList<String>();

        for (int i = 0; i < size; i++) {

            lists.add("t" + (i + 1));

        }

        return lists;

    }

    /**

     *

     * @param pageNum

     * @param pageSize

     * @return  简单分页功能

     */

    public List<String> subList(int pageNum, int pageSize) {

        List<String> lists = init(COUNT);

        int fromIndex = (pageNum - 1) * pageSize;

        int toIndex = fromIndex + pageSize;

        return lists.subList(fromIndex, toIndex);

    }

    public static void main(String[] args) {

        System.out.println("-------- start --------");

        new SubListOperation().output();

        System.out.println("-------- finish --------");

    }

    public void output(){

        int pageNum=2;

        int pageSize=5;

        for(String s:subList(pageNum,pageSize)){

            System.out.println(s);

        }

    }

}

-------- start --------
t6
t7
t8
t9
t10
-------- finish --------

考虑到超出元素个数时异常的情况，做多一步判断。

第二版

    /**

     *

     * @param pageNum

     * @param pageSize

     * @return  简单分页功能

     */

    public List<String> subList(int pageNum, int pageSize) {

        List<String> lists = init(COUNT);

        int fromIndex = (pageNum - 1) * pageSize;

        int toIndex = fromIndex + pageSize;

        int size = lists.size();

        if(fromIndex>=size){

            return new ArrayList<String>();

        }

        return lists.subList(fromIndex, Math.min(size,toIndex));

    }

第三版

package org.sun.java;

import java.util.ArrayList;

import java.util.List;

/**

 *

 * @author Administrator

 * @date 2016年7月16日

 */

public class SubListOperation {

    final static int COUNT = 18;

    public List<String> init(int size) {

        List<String> lists = new ArrayList<String>();

        for (int i = 0; i < size; i++) {

            lists.add("t" + (i + 1));

        }

        return lists;

    }

    /**

     *

     * @param size

     * @return 初始化用户列表

     */

    public List<User> initUser(int size) {

        List<User> lists = new ArrayList<User>();

        for (int i = 0; i < size; i++) {

            lists.add(new User((i + 1), "user" + (i + 1)));

        }

        return lists;

    }

    /**

     *

     * @param pageNum

     * @param pageSize

     * @return 简单分页功能

     */

    public List<User> userSubList(int pageNum, int pageSize) {

        List<User> lists = initUser(COUNT);

        int fromIndex = (pageNum - 1) * pageSize;

        int toIndex = fromIndex + pageSize;

        int size = lists.size();

        if (fromIndex >= size) {

            return new ArrayList<User>();

        }

        return lists.subList(fromIndex, Math.min(size, toIndex));

    }

    public List<String> subList(int pageNum, int pageSize) {

        List<String> lists = init(COUNT);

        int fromIndex = (pageNum - 1) * pageSize;

        int toIndex = fromIndex + pageSize;

        int size = lists.size();

        if (fromIndex >= size) {

            return new ArrayList<String>();

        }

        return lists.subList(fromIndex, Math.min(size, toIndex));

    }

    static class User {

        int id;

        String name;

        public User(int id, String name) {

            super();

            this.id = id;

            this.name = name;

        }

        @Override

        public String toString() {

            return "User [id=" + id + ", name=" + name + "]";

        }

    }

    public static void main(String[] args) {

        System.out.println("-------- start --------");

        // new SubListOperation().outputString();

        new SubListOperation().outputObject();

        System.out.println("-------- finish --------");

    }

    public void outputString() {

        int pageNum = 2;

        int pageSize = 5;

        for (String s : subList(pageNum, pageSize)) {

            System.out.println(s);

        }

    }

    public void outputObject() {

        int pageNum = 2;

        int pageSize = 5;

        for (User s : userSubList(pageNum, pageSize)) {

            System.out.println(s);

        }

    }

}

-------- start --------
User [id=6, name=user6]
User [id=7, name=user7]
User [id=8, name=user8]
User [id=9, name=user9]
User [id=10, name=user10]
-------- finish --------

泛型方法，通用类型实现分页

package org.sun.java;

import java.util.ArrayList;

import java.util.List;

/**

 *

 * @author Administrator

 * @date 2016年7月16日

 */

public class SubListOperation {

    final static int COUNT = 18;

    public List<String> init(int size) {

        List<String> lists = new ArrayList<String>();

        for (int i = 0; i < size; i++) {

            lists.add("t" + (i + 1));

        }

        return lists;

    }

    /**

     *

     * @param size

     * @return 初始化用户列表

     */

    public List<User> initUser(int size) {

        List<User> lists = new ArrayList<User>();

        for (int i = 0; i < size; i++) {

            lists.add(new User((i + 1), "user" + (i + 1)));

        }

        return lists;

    }

    /**

     *

     * @param lists 将被分页展示的列表

     * @param pageNum 页码数

     * @param pageSize 每页条数大小

     * @return

     */

    public <T> List<T> generalPagenation(List<T> lists,int pageNum, int pageSize) {

        int fromIndex = (pageNum - 1) * pageSize;

        int toIndex = fromIndex + pageSize;

        int size = lists.size();

        if (fromIndex >= size) {

            return new ArrayList<T>();

        }

        return lists.subList(fromIndex, Math.min(size, toIndex));

    }

    static class User {

        int id;

        String name;

        public User(int id, String name) {

            super();

            this.id = id;

            this.name = name;

        }

        @Override

        public String toString() {

            return "User [id=" + id + ", name=" + name + "]";

        }

    }

    public static void main(String[] args) {

        System.out.println("-------- start --------");

        new SubListOperation().outputT();

        System.out.println("-------- finish --------");

    }

    public void outputT() {

        int pageNum = 3;

        int pageSize = 5;

        for (Object s : generalPagenation(init(18),pageNum, pageSize)) {

            System.out.println(s);

        }

        System.out.println("---------***---------");

        for (Object s : generalPagenation(initUser(12),pageNum, pageSize)) {

            System.out.println(s);

        }

    }

}

-------- start --------
t11
t12
t13
t14
t15
---------***---------
User [id=11, name=user11]
User [id=12, name=user12]
-------- finish --------

巴特西

Java分页需求

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