feat(class14): 添加数组相关示例代码

- 新增 ArrayDemo1 类，实现随机点名功能
- 新增 ArrayDemo2 类，实现学生成绩输入和统计功能
- 新增 ArrayDemo3 类，实现数组最大值查找功能
- 新增 isPrime 类，判断 101-200 之间的素数

src/class13/isPrime.java

@@ -0,0 +1,24 @@
+package class13;
+
+public class isPrime {
+    public static void main(String[] args) {
+//        101-200
+        int count = 0;
+        for (int i = 101; i < 200; i++) {
+            if (IsPrime(i)) {
+                System.out.println(i);
+                count++;
+            }
+        }
+        System.out.println("===================");
+        System.out.println(count);
+    }
+    public static boolean IsPrime(int n) {
+        for (int i = 2; i < n/2; i++) {
+            if (n % i == 0) {
+                return false;
+            }
+        }
+        return true;
+    }
+}

src/class14/ArrayDemo1.java

@@ -0,0 +1,14 @@
+package class14;
+
+public class ArrayDemo1
+{
+    public static void main(String[] args) {
+        randomCall();
+    }
+    public static void randomCall()
+    {
+        String[] names = {"张三","李四","王五","赵六","小七"};
+        int index = (int)(Math.random() * names.length);
+        System.out.println(names[index]);
+    }
+}

src/class14/ArrayDemo2.java

@@ -0,0 +1,37 @@
+package class14;
+
+import java.util.Scanner;
+
+public class ArrayDemo2 {
+    public static void main(String[] args) {
+        inputScore();
+    }
+    public static void inputScore()
+    {
+        int[] scores = new int[8];
+        Scanner scanner = new Scanner(System.in);
+        for(int i = 0;i < scores.length;i++)
+        {
+            System.out.println("请输入第"+(i+1)+"个同学的分数：");
+            scores[i] = scanner.nextInt();
+        }
+        double allScore = 0;
+        double maxScore = scores[0];
+        double minScore = scores[0];
+
+        for (double score : scores) { //作用：遍历数组中的元素，增强 for
+            allScore += score;
+            if (score > maxScore) {
+                maxScore = score;
+            } else if (score < minScore) {
+                minScore = score;
+            }
+
+        }
+        System.out.println("平均分：" + allScore / scores.length);
+        System.out.println("最高分：" + maxScore);
+        System.out.println("最低分：" + minScore);
+        System.out.println("===================");
+
+    }
+}

src/class14/ArrayDemo3.java

@@ -0,0 +1,20 @@
+package class14;
+
+public class ArrayDemo3 {
+    public static void main(String[] args) {
+        int[] arr = {10,20,30,40,50};
+        int max=getMax(arr);
+        System.out.println("The maximum value is: " + max);
+    }
+    public static int getMax(int[] arr){
+        int max = arr[0];
+        for (int i = 1; i < arr.length; i++) {
+            int data = arr[i]; //减少查找性能开销
+            if(max < data){
+                max = data;
+            }
+        }
+        return max;
+    }
+
+}