JAVA语言程序设计课后习题----第八单元解析（仅供参考）

1　　本题主要考的是方法的克隆，与c++里面的拷贝有点相似，具体看书本p147

 import java.util.Objects;
 
 public class Square implements Cloneable{
     private int length;
 
     public Square(int length) {
         this.length = length;
     }
 
     @Override
     public String toString() {
         return "Square[" +
                 "length=" + length +
                 ']';
     }
 
     @Override
     public boolean equals(Object o) {
         if (this == o) return true;
         if (o == null || getClass() != o.getClass()) return false;
         Square square = (Square) o;
         return length == square.length;
     }
 
     @Override
     public int hashCode() {
         return Objects.hash(length);
     }
 
     public static void main(String[] args) throws CloneNotSupportedException{
         Square s1=new Square(100);
         Square  s2=(Square)s1.clone();
         System.out.println(s1==s2);
         System.out.println(s1.equals(s2));
         System.out.println(s2.toString());
 
     }
 }

2　　本题水题，主要就是考数组，把产生的需求数存在数组里

 public class Suiji {
     public static int a[]=new int[6];
     public static void main(String[] args) {
         Suiji s=new Suiji();
         System.out.println("随机产生1000个1-6的数");
         s.stc(6);
 
         for (int i = 1; i <=6 ; i++) {
             System.out.println(i+"的概率是"+(a[i-1]*1.0/1000)*100+"%");
         }
         System.out.println("****************************");
         System.out.println("随机产生1000个1-1000的数");
         for (int i = 0; i < a.length; i++) {
             a[i]=0;
         }
         s.stc(1000);
         for (int i = 1; i <=6 ; i++) {
             System.out.println(i+"的概率是"+(a[i-1]*1.0/1000)*100+"%");
         }
 
     }
     public void stc(int num){
         for (int i = 0; i <1000 ; i++) {
             switch ((int)(Math.random()*num+1)){
                 case 1:a[0]++;
                     break;
                 case 2:a[1]++;
                     break;
                 case 3:a[2]++;
                     break;
                 case 4:a[3]++;
                     break;
                 case 5:a[4]++;
                     break;
                 case 6:a[5]++;
                     break;
             }
         }
     }
 }

3　　本题注意sinx x是弧度即可

 public class Area {
     public static void main(String[] args) {
         float a=4.0f,b=5.0f;
 
         float t= (float) Math.sin(30*(Math.PI/180));
        // System.out.println("三角形的面积为:"+(1*1.0/2)*a*b*t);
         System.out.println(((1*1.0/2)*a*b*t));
     }
 
 }

4　　本题只要记得如何求最大值、最小值的封装方法即可（MAX_VALUE、MIN_VALUE）

 public class Baozhuang {
     //    Integer integer;
     public static void main(String[] args) {
         Integer integer = null;
         System.out.println("Integer的最大值"+integer.MAX_VALUE+"\t"+"Integer的最小值"+integer.MIN_VALUE);
         Long l=null;
         System.out.println("Long的最大值"+l.MAX_VALUE+"\t"+"Long的最小值"+l.MIN_VALUE);
         Float f=null;
         System.out.println("Float的最大值"+f.MAX_VALUE+"\t"+"Float的最小值"+f.MIN_VALUE);
         Double d=null;
         System.out.println("Double的最大值"+d.MAX_VALUE+"\t"+"Double的最小值"+d.MIN_VALUE);
         Character character=null;
         System.out.println(" Character的最大值"+character.MAX_VALUE+"\t"+" Character的最小值"+character.MIN_VALUE);
         Byte b=null;
         System.out.println(" Byte的最大值"+b.MAX_VALUE+"\t"+" Byte的最小值"+b.MIN_VALUE);
         Short s=null;
         System.out.println("Short的最大值"+s.MAX_VALUE+"\t"+" Short的最小值"+s.MIN_VALUE);
 
     }
 }

5　　本题自行百度查看

6　　本题水题，plusDays就是给当前对象增加几天

 import java.text.ParseException;
 import java.time.LocalDate;
 public class ch06 {
     public static void main(String[] args) throws ParseException {
         LocalDate pday=LocalDate.of(2017,1,1).plusDays(256);
         System.out.println(pday);
     }
 }

7　　本题主要就是知道如何求天数，对什么值求模

 import java.text.ParseException;
 import java.text.SimpleDateFormat;
 import java.util.Date;
 import java.util.Scanner;
 
 public class ch07 {
     public static void main(String[] args) throws ParseException {
         Scanner input =new Scanner(System.in);
         String dbtime1 = input.next();  //第二个日期
         String dbtime2 = input.next();  //第一个日期
 //算两个日期间隔多少天
         SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");
         Date date1 = format.parse(dbtime1);
         Date date2 = format.parse(dbtime2);
 
         int a = (int) ((date1.getTime() - date2.getTime()) / (1000*3600*24));
         System.out.println(a);
     }
 }

8　　本题具体自行查看书本p159

 import java.time.LocalDate;
 import java.time.format.TextStyle;
 import java.util.Locale;
 import java.util.Scanner;
 
 public class PromtCalendar {
     public static void main(String[] args) {
         Scanner input = new Scanner(System.in);
         System.out.println("输入一个年份(如2018)：");
         int year = input.nextInt();
 
         for (int j = 1; j <=12; j++) {
             //        返回本月第一天
             LocalDate dates = LocalDate.of(year,j, 1);
             String monthName = dates.getMonth().getDisplayName(TextStyle.FULL, Locale.getDefault());
 //        返回当月的天数
             int dayOFmonth = dates.lengthOfMonth();
             System.out.println(year + "年     " + monthName);
             System.out.println("-------------------------------");
             System.out.printf("%4s%3s%3s%3s%3s%3s%3s%n", "一", "二", "三", "四", "五", "六", "日");
             int dayOfWeek = dates.getDayOfWeek().getValue();
             for (int i = 2; i <= dayOfWeek; i++) {
                 System.out.printf("%4s", " ");
             }
             for (int i = 1; i <= dayOFmonth; i++) {
                 System.out.printf("%4d", i);
                 if ((dayOfWeek + i - 1) % 7 == 0)
                     System.out.println();
             }
             System.out.println();
         }
     }
 }

9　　本题主要考的数组里面值的存入问题，也可以用if语句逐一进行判断，注意要月份和天数都要满足

 import java.util.Scanner;
 
 public class xingzuo {
    /* public static void main(String[] args) {
         Scanner input = new Scanner(System.in);
         System.out.println("输入一个年份(如2018)：");
 int year=input.nextInt();
         int month = input.nextInt();
 //       输入天数
         int day = input.nextInt();
         LocalDate dates3 = LocalDate.of(year, month, day).plusDays(30);
         //dates3.plusDays(30);
         System.out.println(dates3);
 
         LocalDate[] desk = {LocalDate.of( 0,3, 20), LocalDate.of(0, 4, 20),
                 LocalDate.of(0, 4, 19), LocalDate.of(0, 4, 21),
                 LocalDate.of(0, 5, 20), LocalDate.of(0, 6, 22),
                 LocalDate.of(0, 6, 21), LocalDate.of(0, 7, 23),
                 LocalDate.of(0, 7, 22), LocalDate.of(0, 8, 23),
                 LocalDate.of(0, 8, 22), LocalDate.of(0, 9, 24),
                 LocalDate.of(0, 9, 22), LocalDate.of(0, 10, 24),
                 LocalDate.of(0, 10, 23), LocalDate.of(0, 11, 23),
                 LocalDate.of(0, 11, 22), LocalDate.of(0, 12, 22),
                 LocalDate.of(0, 12, 21), LocalDate.of(0, 1, 20),
                 LocalDate.of(0, 1, 19), LocalDate.of(0, 2, 19),
                 LocalDate.of(0, 2, 18), LocalDate.of(0, 3, 21)};
 
         if (dates3.isAfter(desk[0]) && dates3.isBefore(desk[1])) {
 
             System.out.println("白羊座" );
         }
         else if (dates3.isAfter(desk[2]) && dates3.isBefore(desk[3])){
             System.out.println("金牛座");
         }
         else if (dates3.isAfter(desk[4]) && dates3.isBefore(desk[5])){
             System.out.println("双子");
         }
         else if (dates3.isAfter(desk[6]) && dates3.isBefore(desk[7])){
             System.out.println("巨蟹");
         }
         else if (dates3.isAfter(desk[8]) && dates3.isBefore(desk[9])){
             System.out.println("狮子");
         }
         else if (dates3.isAfter(desk[10]) && dates3.isBefore(desk[11])){
             System.out.println("处女");
         }
         else if (dates3.isAfter(desk[12]) && dates3.isBefore(desk[13])){
             System.out.println("天平");
         }
         else if (dates3.isAfter(desk[14]) && dates3.isBefore(desk[15])){
             System.out.println("天蝎");
         }
         else if (dates3.isAfter(desk[16]) && dates3.isBefore(desk[17])){
             System.out.println("射手");
         }
         else if (dates3.isAfter(desk[18]) && dates3.isBefore(desk[19])){
             System.out.println("摩羯");
         }
         else if (dates3.isAfter(desk[20]) && dates3.isBefore(desk[21])){
             System.out.println("水平");
         }
         else if (dates3.isAfter(desk[22]) && dates3.isBefore(desk[23])){
             System.out.println("双鱼");
         }
     }*/
 
     public static void main(String[] args) {
 
         Scanner input = new Scanner(System.in);
         System.out.println("请输入出生日期如（5 20）");
         System.out.println(
                 getConstellation(input.nextInt(),input.nextInt())
         );
     }
     private final static int[] dayArr = new int[] { 20, 19, 21, 20, 21, 22, 23, 23, 23, 24, 23, 22 };
     private final static String[] constellationArr = new String[] { "摩羯座", "水瓶座", "双鱼座", "白羊座", "金牛座", "双子座", "巨蟹座", "狮子座", "处女座", "天秤座", "天蝎座", "射手座", "摩羯座" };
     public static String getConstellation(int month, int day) {
         return day < dayArr[month - 1] ? constellationArr[month - 1] : constellationArr[month];
     }
 }