java基础demo， 控制台打印菱形，编程规范及面向对象思想。

java基础练习，通过入口函数随机一个N值，打印出一个相应的菱形

思路清晰，画图即可。

对了，方法多种，下列非最优解，欢迎探讨。

1、CreateStar 类，用于创建菱形

package practice.print.star;

import com.savvy.wit.web.commons.util.DateUtil;
import practice.print.star.business.Star;

import java.util.*;

public class CreateStar {

    private static int xLength = 0 ; //行高度
    private static int yLength = 0 ; //列高度
    private static Map< Integer,List<Star> > map = new HashMap< Integer,List<Star> >(); // 存
    private int num = 0; //打印多少行
    private boolean odevity = false; //默认奇数
    public CreateStar() {
        //
        System.out.println(DateUtil.getNow("yyyy-MM-dd HH:mm:ss")+"\t===>\t"+this.getClass().getName()+":constructor" );
    }

    public CreateStar(int num) {
        System.out.println(DateUtil.getNow("yyyy-MM-dd HH:mm:ss")+"\t===>\t"+this.getClass().getName()+":constructor" );
        this.num = num;
        this.odevity = num % 2 == 0 ? true : false;
        this.xLength = num % 2 != 0 ? num : (num-1);
        this.yLength = num;
    }

    public void setnum(int num) {
        this.num = num;
    }

    public Map<Integer,List<Star>> getStars() {
        if(yLength == 0 && num != 0) {
            new CreateStar(this.num);
        }
        int start = startIndex(xLength);  // 起始点
        int invert;  //反转偏移

        for ( int y =0; y < yLength; y ++ ) {
            List list = new ArrayList();
            int index = 0;  //当前游标
            if(this.odevity) invert = 2*y >= xLength  ? (xLength  - y) : 0; //奇偶性决定反转游标偏移量
            else invert = 2*y >= xLength  ? (xLength -1 - y) : 0;

            for( int x = 0; x < xLength; x++ ) {
                index ++;
                Star star = new Star();
                star.setId(UUID.randomUUID().toString().replaceAll("-"," "));
                if(2*y >= xLength) { //反转
                    if( index >= (start - invert) && index <= (start + invert) ) {
                        star.setCode(1);
                    }else {
                        star.setCode(0);
                    }
                }else if( index >= (start - y) && index <= (start + y) ) {
                    star.setCode(1);
                }else {
                    star.setCode(0);
                }
                list.add(star);
            }

            map.put(y,list);
        }
        return map;
    }

    /**
     * 起始点坐标
     * @param width
     * @return
     */
    private static int startIndex( int width ) {
        return width%2 ==0 ? width/2 : width/2+1;
    }

}

2、PrintStars 类，用于打印菱形

package practice.print;
import com.savvy.wit.web.commons.util.DateUtil;
import practice.print.star.CreateStar;
import practice.print.star.business.Star;

import java.util.*;

public class PrintStars {

    private static int height = 0;
    public static void main(String[] args) {
        height =  Integer.parseInt(  String.valueOf(new Date().getTime()).substring(11,12) ) ;
//        CreateStar createStar = new CreateStar();
//        createStar.setnum(height < 1 ? 1 : height);
//        new PrintStars().printStarsMap(createStar.getStars());
        System.out.println(height);
        new PrintStars().printStarsMap ( new CreateStar(height < 1 ? 1 : height).getStars() );
    }

    public void printStarsMap (Map<Integer,List<Star>> map) {
        System.out.println(DateUtil.getNow("yyyy-MM-dd HH:mm:ss")+"\t===>\t"+this.getClass().getName());
        for (int h=0; h < (height == 0 ? 1 : height); h++) {
            for(Star star : map.get(h)) {
                System.out.print(star.getStar());
            }
            System.out.println();
//           Iterator iterator = map.get(h).iterator();
//           while(iterator.hasNext()) {
//               if(iterator.next() instanceof Star) {
//                   Star star = (Star) iterator.next();
//                   System.out.println( star.getStar() );
//               }
//           }
        }
    }
}

3、Star 类，打印格式

package practice.print.star.business;
import java.io.Serializable;

public class Star implements Serializable {

    private static final String STAR = "☆";

    private String id;
    // 0 空格  1 ☆
    private int code;

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }

    public void setCode(int code) {
        this.code = code;
    }

    public String getStar () {
        return code == 0 ? "  " : STAR ;
    }

    public String getStar (String star) {
        if( code == 0) {
            StringBuilder sb = new StringBuilder("");
            for (int i = 0; i < star.length(); i++) {
                sb.append(" ");
            }
            return  sb.toString();
        }else {
            return star;
        }
    }
}

4、DateUtil，常用时间处理工具类

package com.savvy.wit.web.commons.util;

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;
import java.util.Random;

/**
 * Created by aj907 on 2018/4/27.
 */
public class DateUtil {

    private static Random random = new Random();
    private static String pool = "qwertyuiopasdfghjklzxcvbnmQWERTYUIOPASDFGHJKLZXCVBNM" ;

    /**
     * 根据系统时间随机获取一个编号
     * @param len
     * @return
     */
    public static Long createNumber(int len){
        StringBuilder sb = new StringBuilder(getNow("yyyyMMddHHmmss"));
        for(int i = 0 ; i++<len ;){
            sb.append(random(10));
        }
        return Long.parseLong(sb.toString());
    }

    /**
     * 根据系统时间随机获取一个编号
     * @param len
     * @return
     */
    public static String createCode(int len){
        StringBuilder sb = new StringBuilder(getNow("yyyyMMddHHmmss"));
        for(int i = 0 ; i++<len ;){
            sb.append( pool.charAt(random(pool.length()) ));
        }
        return sb.toString();
    }

    /**
     * 获取处理耗时
     * @param start
     * @param end
     * @return
     */
    public static String getTimeConsuming( long start,long end){
        long time=end-start;//计算插入耗时
        return "耗时:\t"+(time>10000?getTime(time, "mm分ss秒"):time+"毫秒");
    }

    /**
     * 获取当前系统时间
     * @param format 日期转化格式
     *               建议格式:yyyy-MM-dd HH:mm:ss
     * @return String 日期
     */
    public static String getNow(String format){
        return new SimpleDateFormat(format).format(new Date());
    }
    public static String getNow(){
        return new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(new Date());
    }
    /**
     * 毫秒值转为 format类型的时间字符
     * @param time
     * @param format
     * @return
     */
    public static String getTime(long time,String format){
        Calendar calendar=Calendar.getInstance();
        calendar.setTimeInMillis(time);
        return new SimpleDateFormat(format).format(calendar.getTime());
    }

    /**
     * 获取系统当前毫秒值
     * @return
     */
    public static long getTime(){
        return System.currentTimeMillis();
    }

    /**
     * 获取时间
     *
     * @param str 字符串日期格式 2017-06-26 13:21:12
     *                     统一解析格式 yyyy-MM-dd HH:mm:ss
     * @return date
     */
    public static Date getDate(String str){
        String format="yyyy-MM-dd HH:mm:ss";
        SimpleDateFormat sdf=new SimpleDateFormat(format);
        Date date=null;
        try {
            date=sdf.parse(str);
        } catch (ParseException e) {
            e.printStackTrace();
        }
        return date;
    }

    /**
     * 获取随机数
     * @param ran
     * @return
     */
    public static int random(int ran){
        return random.nextInt(ran);
    }

结果图