学习完一维数组，再进行多维数组的学习会更加容易。多维数组可以解决更为复杂的问题，在用法上与一维数组也有很多类似的地方。下面先从二维数组的基本用法展示开始讲解，然后再进行升级。
示例一：二维数组的基本操作。
运行效果如图所示：![《Java基本功练习八（多维数组[二维、三维、模拟评卷系统、九宫格验证]）》](http://ddrvcn.oss-cn-hangzhou.aliyuncs.com/2019/3/f2qYRf.jpeg)
实现的源代码如下：
package Blog;
import java.util.Scanner;
public class blogTryProject {
//二维数组基本操作
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
int[][] matrix = new int[5][5];
System.out.println(matrix.length+" rows and "
+matrix[0].length+" columns");
//随机产生5*5数组
for(int row = 0;row < matrix.length;row++){
for(int columns = 0;columns < matrix[row].length;columns++){
matrix[row][columns] = (int)(Math.random()*20);
System.out.printf("%3d ",matrix[row][columns]);
}
System.out.println();
}
//按列求和
for(int columns = 0;columns < matrix[0].length;columns++){
int total = 0;
for(int row = 0;row < matrix.length;row++)
total += matrix[row][columns];
System.out.println("Sum for column "+columns+" is "+total);
}
//按行求和
for(int row = 0;row < matrix.length;row++){
int total = 0;
for(int columns = 0;columns < matrix[row].length;columns++)
total += matrix[row][columns];
System.out.println("Sum for row "+row+" is "+total);
}
//求最大的一行
int maxSum = 0;
int indexOfMax = 0;
for(int columns = 0;columns < matrix[0].length;columns++){
maxSum += matrix[0][columns];
}
for(int row = 1;row < matrix.length;row++){
int maxThisRow = 0;
for(int columns = 0;columns < matrix[0].length;columns++)
maxThisRow += matrix[row][columns];
if(maxThisRow > maxSum){
maxSum = maxThisRow;
indexOfMax = row;
}
}
System.out.println("Row "+indexOfMax+" has the maximun sum of "+maxSum);
//随意打乱数组的元素
for(int row = 1;row < matrix.length;row++){
for(int columns = 0;columns < matrix[0].length;columns++){
int i = (int)(Math.random()*matrix.length);
int j = (int)(Math.random()*matrix[i].length);
int temp = matrix[row][columns];
matrix[row][columns] = matrix[i][j];
matrix[i][j] = matrix[row][columns];
}
}
//打印打乱后的数组元素
for(int row = 1;row < matrix.length;row++){
for(int columns = 0;columns < matrix[0].length;columns++)
System.out.printf("%3d",matrix[row][columns]);
System.out.println();
}
}
}
学会了二维数组的基本用法，就要检验一下是否掌握了，以示例二的题目进行检验。
示例二：显示二维空间所有距离最短的点对。程序要求输入二维点的个数，及每个二维点，然后求出这些二维点相互之间距离最短的所有点对。
运行效果如右所示：![《Java基本功练习八（多维数组[二维、三维、模拟评卷系统、九宫格验证]）》](http://ddrvcn.oss-cn-hangzhou.aliyuncs.com/2019/3/UV3aQ3.jpeg)
![《Java基本功练习八（多维数组[二维、三维、模拟评卷系统、九宫格验证]）》](http://ddrvcn.oss-cn-hangzhou.aliyuncs.com/2019/3/QzyY3e.jpeg)
![《Java基本功练习八（多维数组[二维、三维、模拟评卷系统、九宫格验证]）》](http://ddrvcn.oss-cn-hangzhou.aliyuncs.com/2019/3/NfQ7fa.jpeg)
实现的源代码如下图所示：
package Blog;
import java.util.Scanner;
public class blogTryProject {
//找出距离最短的所有点对
public static void main(String[]args){
Scanner input = new Scanner(System.in);
System.out.print("Enter the number of points: ");//输入点个数
int numberOfPoints = input.nextInt();
double[][]points = new double[numberOfPoints][2];//输入每个点
System.out.print("Enter "+numberOfPoints+" points: ");
for(int i = 0;i <points.length;i++){
points[i][0] = input.nextDouble();
points[i][1] = input.nextDouble();
}
int[] p1 = new int[numberOfPoints];//目标点下标数组
int[] p2 = new int[numberOfPoints];
int ii = 0,jj = 0;
double shortestDistance = distance(points[0][0],points[0][1],
points[1][0],points[1][1]);//初始化点对距离
//找出最短距离值
for(int i = 0;i < points.length;i++){
for(int j = i+1;j <points.length;j++){
double distance = distance(points[i][0],points[i][1],
points[j][0],points[j][1]);
if(shortestDistance > distance)
shortestDistance = distance;
}
}
//记录最短距离点对下标
for(int i = 0;i < points.length;i++){
for(int j = i+1;j <points.length;j++){
double distance = distance(points[i][0],points[i][1],
points[j][0],points[j][1]);
if(shortestDistance == distance){
p1[ii++] = i;
p2[jj++] = j;
shortestDistance = distance;
}
}
}
//打印最短距离点对
for(int i = 0;i < ii;i++){
System.out.println("The closest two points are "+"("+points[p1[i]][0]+","+
points[p1[i]][1]+") and ("+points[p2[i]][0]+","+points[p2[i]][1]+")");
}
}
public static double distance(double x1,double y1,double x2,double y2){
return Math.sqrt((x2-x1)*(x2-x1)+(y1-y2)*(y1-y2));
}
}
学完了二维数组，再看看三维数组的几个例子。
示例三：三维数组猜生日的小程序。即问用户五个问题，只需回答Yes或No，就可猜出用户生日的日期。
运行效果如图所示：![《Java基本功练习八（多维数组[二维、三维、模拟评卷系统、九宫格验证]）》](http://ddrvcn.oss-cn-hangzhou.aliyuncs.com/2019/3/iqUjUn.png)
实现的源代码如下所示：
package Blog;
import java.util.Scanner;
public class blogTryProject {
//猜生日的小程序
public static void main(String[]args){
int day = 0;
int answer;
int[][][] dates = {
{{ 1, 3, 5, 7},
{ 9,11,13,15},
{17,19,21,23},
{25,27,29,31}},
{{ 2, 3, 6, 7},
{10,11,14,15},
{18,19,22,23},
{26,27,30,31}},
{{ 4, 5, 6, 7},
{12,13,14,15},
{20,21,22,23},
{28,29,30,31}},
{{ 8, 9,10,11},
{12,13,14,15},
{24,25,26,27},
{28,29,30,31}},
{{16,17,18,19},
{20,21,22,23},
{24,25,26,27},
{28,29,30,31}}};
Scanner input = new Scanner(System.in);
System.out.println("例如你的生日是25日！如实回答以下5个问题。");
for(int i = 0;i < 5;i++){
System.out.println("Is your birthday in Set"+(i+1)+"?");
for(int j = 0;j < 4;j++){
for(int k = 0;k < 4;k++)
System.out.printf("%4d",dates[i][j][k]);
System.out.println();
}
System.out.print("Enter 0 for No and 1 for Yes: ");
answer = input.nextInt();
if(answer == 1)
day += dates[i][0][0];
}
System.out.println("Your birthday day is "+day);
}
}
学完三维数组，相应的给出一个示例作为练习。
示例四：模拟评卷系统，输出学生的排名。程序要求输入学生人数8和题目数10，并随机产生每个学生的答案；再给出正确答案进行改卷，最后统计每个学生做对题目的数目，进行排名输出。
运行效果如图所示：![《Java基本功练习八（多维数组[二维、三维、模拟评卷系统、九宫格验证]）》](http://ddrvcn.oss-cn-hangzhou.aliyuncs.com/2019/3/rMJRNb.png)
实现源代码如下：
package Blog;
import java.util.Scanner;
import java.util.Arrays;
public class blogTryProject {
//多选题测验评分，并排名输出
public static void main(String[]args){
final int NUMBER_OF_STUDENT = 8;//学生数目
final int NUMBER_OF_TIMU = 10;//题目数目
char[][] student = new char[NUMBER_OF_STUDENT][NUMBER_OF_TIMU];//打印学生答案
student = printStudentAnswer(NUMBER_OF_STUDENT,NUMBER_OF_TIMU);
char[] key = {'D','B','D','C','C','D','A','E','A','D'};//打印正确答案
printCorrectAnswer(NUMBER_OF_TIMU,key);
int[] count = new int[NUMBER_OF_STUDENT];//模拟改卷，并评分
count = printGaiJuanPingFen(student,key,count);
int[] bianHaoOfStudent = new int[NUMBER_OF_STUDENT];//学生排名输出
printPaiMing(bianHaoOfStudent,count);
}
public static char[][] printStudentAnswer(int numS,int numT){
System.out.println("学生给出的题目答案如下");
System.out.print(" 题号：");
for(int i = 0;i < numT;i++)
System.out.printf("%d ",i);
System.out.println();
char[][] student = new char[numS][numT];
for(int i = 0;i < student.length;i++){
System.out.printf("Student %2d ",i);
for(int j = 0;j < student[0].length;j++){
char c = (char)('A'+Math.random()*('E'-'A'+1));
student[i][j] = c;
System.out.printf("%2c",student[i][j]);
}
System.out.println();
}
return student;
}
public static void printCorrectAnswer(int numT,char[] key){
System.out.print("题目正确答案:");
for(int i = 0;i < numT;i++)
System.out.printf("%c ",key[i]);
System.out.println();
}
public static int[] printGaiJuanPingFen(char[][] student,char[] key,int[] count){
for(int i = 0;i < student.length;i++){
for(int j = 0;j < student[0].length;j++){
if(student[i][j] == key[j])
count[i]++;
}
System.out.printf("Student %2d 做对了 %2d 道题\n",i,count[i]);
}
return count;
}
public static void printPaiMing(int[] bianHaoOfStudent,int[] count){
for(int i = 0;i < bianHaoOfStudent.length;i++)
bianHaoOfStudent[i] = i;
insertSort(count,bianHaoOfStudent);//排名函数
for(int i= 0;i < count.length;i++)
System.out.println("Student "+bianHaoOfStudent[i]+" 排名第 "+(i+1)
+" (做对"+count[i]+"题)");
}
public static void insertSort(int[] chars,int[] bianHaoOfStudent){
System.out.println("成绩排名如下：");
for(int i = 1;i < chars.length;i++){
for(int j = 0;j < i;j++){
if(chars[i] > chars[j]){
int temp = chars[i];
chars[i] = chars[j];
chars[j] = temp;
int temp1 = bianHaoOfStudent[i];
bianHaoOfStudent[i] = bianHaoOfStudent[j];
bianHaoOfStudent[j] = temp1;
}
}
}
}
}
作为练习，童鞋们可以将此题改为任意个学生，任意个题目，手工录入正确答案，然后考虑并列的排名。请童鞋们自行练习！
示例五：九宫格的一种验证方法。即是验证某一种输入是否满足九宫格的要求，满足显示”Valid solution“，否则显示”Invalid solution“。
运行效果如图所示：![《Java基本功练习八（多维数组[二维、三维、模拟评卷系统、九宫格验证]）》](http://ddrvcn.oss-cn-hangzhou.aliyuncs.com/2019/3/MB7bA3.jpeg)
![《Java基本功练习八（多维数组[二维、三维、模拟评卷系统、九宫格验证]）》](http://ddrvcn.oss-cn-hangzhou.aliyuncs.com/2019/3/ZRzQru.png)
实现的源代码如下所示：
package Blog;
import java.util.Scanner;
import java.util.Arrays;
public class blogTryProject {
//九宫格简化版本，验证输入的答案是否正确
public static void main(String[]args){
Scanner input = new Scanner(System.in);
int[][] grid =readASolution();
System.out.println(isValid(grid) ? "Valid solution" : "Invalid solution");
}
public static int[][] readASolution(){
Scanner input = new Scanner(System.in);
System.out.println("Enter a SuDu puzzle solution:");
int [][] grid = new int[9][9];
for(int i = 0;i < 9;i++)
for(int j = 0;j < 9;j++)
grid[i][j] = input.nextInt();
return grid;
}
public static boolean isValid(int[][] grid){
//检查每行是否包含1到9
for(int i = 0;i < 9;i++)
if(!is1To9(grid[i]))
return false;
//检查每列是否包含1到9
for(int j = 0;j < 9;j++){
int[] column = new int[9];
for(int i = 0;i < 9;i++)
column[i] = grid[i][j];
if(!is1To9(column))
return false;
}
//
for(int i = 0;i < 3;i++){
for(int j = 0; j < 3;j++){
int k = 0;
int[] list = new int[9];
for(int row = i*3;row < i*3 + 3;row++)
for(int column = j*3;column < j*3 +3;column++)
list[k++] = grid[row][column];
if(!is1To9(list))
return false;
}
}
return true;
}
public static boolean is1To9(int[] list){
int[] temp = new int[list.length];
System.arraycopy(list, 0, temp, 0, list.length);
java.util.Arrays.sort(temp);
for(int i = 0;i < 9;i++)
if(temp[i] != i + 1)
return false;
return true;
}
}
总结：多维数组的灵活运用可以解决很多复杂的问题。
