从零自学Java-7.使用数组存储信息

1.创建数组；

2.设置数组的大小；

3.为数组元素赋值；

4.修改数组中的信息；

5.创建多维数组；

6.数组排序。

程序SpaceRemover：显示输入字符串，并将其中所有的空格字符替换为句点字符。

 package com.jsample;
 
 public class SpaceRemover {
     public static void main(String[] args){
         String mostFamous = "Rudolph the Red-nosed Reindeer";
         char[] mfl = mostFamous.toCharArray();//将文本中的每一个字符存储到数组的一个元素中
         for (int dex = 0; dex < mfl.length; dex++){
             char current = mfl[dex];
             if (current != ' '){
                 System.out.print(current);
             }
             else
                 System.out.print('.');
         }
         System.out.println();
     }
 }

输出：

Rudolph.the.Red-nosed.Reindeer

程序NameSorter：将字符串数组中的姓名按字母序排序

 package com.jsample;
 
 import java.util.*;
 
 public class NameSorter {
     public static void main(String[] args){
         String names[] ={"Glimmer", "Marvel", "Rue", "Clove",
                 "Thresh", "Foxface", "Cato", "Peeta", "Katniss"};
         System.out.println("The origin order:");
         for(int i = 0; i < names.length; i++){
             System.out.println(i + ": " + names[i]);
         }
         System.out.println();
         Arrays.sort(names);
         System.out.println("The new order:");
         for(int i = 0; i < names.length; i++){
             System.out.println(i + ": " + names[i]);
         }
         System.out.println();
     }
 }

输出：

The origin order:
0: Glimmer
1: Marvel
2: Rue
3: Clove
4: Thresh
5: Foxface
6: Cato
7: Peeta
8: Katniss

The new order:
0: Cato
1: Clove
2: Foxface
3: Glimmer
4: Katniss
5: Marvel
6: Peeta
7: Rue
8: Thresh

程序Wheel：用来统计字母在不同短语或表达中出现的频率，并使用数组来存放每个字母出现的字数。当程序运行时，它将显示每个字母在短语中出现的次数。

 package com.jsample;
 
 public class Wheel {
     public static void main(String[] args){
         String[] phrase={
                 "A STITCH IN TIME SAVES NINE",
                 "DON'T EAT YELLOW SNOW",
                 "JUST DO IT",
                 "EVERY GOOD BOY DOES FINE",
                 "I WANT MY MTV",
                 "I LIKE IKE",
                 "PLAY IT AGAIN,SAM",
                 "FROSTY THE SNOWMAN",
                 "ONE MORE FOR THE ROAD",
                 "HOME FIELD ADVANTAGE",
                 "VALENTINE'S DAY MASSACRE",
                 "GROVER CLEVELAND OHIO",
                 "SPAGHETTI WESTERN",
                 "AQUA TEEN HUNGER FORCE",
                 "IT'S A WONDERFUL LIFE"
         };
         int[] letterCount = new int[26];
         for(int count = 0; count < phrase.length; count++){
             String current = phrase[count];
             char[] letters = current.toCharArray();
             for (int count2 = 0; count2 < letters.length; count2++){
                 char left = letters[count2];
                 if ((left >= 'A') & (left <= 'Z')){
                     letterCount[left - 'A']++;
                 }
             }
         }
         for (char count = 'A'; count <= 'Z'; count++){
             System.out.print(count + ": " +
                 letterCount[count - 'A'] +
                 " ");
             if (count == 'M'){
                 System.out.println();
             }
         }
         System.out.println();
     }
 }

输出：

A: 22 B: 1 C: 4 D: 10 E: 33 F: 7 G: 6 H: 7 I: 18 J: 1 K: 2 L: 10 M: 8
N: 19 O: 20 P: 2 Q: 1 R: 12 S: 15 T: 20 U: 4 V: 7 W: 6 X: 0 Y: 7 Z: 0

程序ClassGradeDataBase：使用多维数组存储学生的成绩，第一维是学生编号，第二维是每个学生的成绩。显示全部学生的平均成绩以及每个学生的平均成绩。

 package com.jsample;
 
 import java.util.*;
 
 public class ClassGradeDataBase {
     public static void main(String[] args){
         Random generator = new Random();
         int[][] dataBase = new int[10][4];
         long i = 0;
         long sum = 0;
         for (int index = 0; index < 10; index++){
             dataBase[index][0] = index + 1;
             dataBase[index][1] = generator.nextInt()/10000000;
             dataBase[index][2] = generator.nextInt()/10000000;
             dataBase[index][3] = generator.nextInt()/10000000;
             dataBase[index][1] = Math.abs(dataBase[index][1]);
             dataBase[index][2] = Math.abs(dataBase[index][2]);
             dataBase[index][3] = Math.abs(dataBase[index][3]);
             i = (dataBase[index][1] + dataBase[index][2] + dataBase[index][3]);
             sum += i;
             System.out.println("No."+ dataBase[index][0] + "'s average grades:" + i/3);
         }
         System.out.println("The average grades of all students:" + sum/30);
     }
 }

输出：

No.1's average grades:140
No.2's average grades:183
No.3's average grades:103
No.4's average grades:91
No.5's average grades:136
No.6's average grades:136
No.7's average grades:91
No.8's average grades:107
No.9's average grades:127
No.10's average grades:156
The average grades of all students:127

程序Mod13Array：将能被13整除的前400个数存储到数组中。

 package com.jsample;
 
 public class Mod13Array {
     public static void main(String[] args){
         int[] array = new int [401];
         int index = 0;
         for(int flag = 1; flag <= 400; index++){
             if(index % 13 == 0) {
                 flag++;
                 array[flag-1] = index;
                 System.out.println(index + " ");
             }
         }
     }
 }

输出：
0

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