测试不同时间复杂度的程序运行时间Java版本测试代码

problems/前序/On的算法居然超时了，此时的n究竟是多大？.md

@@ -206,7 +206,62 @@ int main() {
     }
 }
 
+```
 
+
+Java版本
+```Java
+import java.util.Scanner;
+
+public class TimeComplexity {
+    // o(n)
+    public static void function1(long n) {
+        System.out.println("o(n)算法");
+        long k = 0;
+        for (long i = 0; i < n; i++) {
+            k++;
+        }
+    }
+
+    // o(n^2)
+    public static void function2(long n) {
+        System.out.println("o(n^2)算法");
+        long k = 0;
+        for (long i = 0; i < n; i++) {
+            for (long j = 0; j < n; j++) {
+                k++;
+            }
+        }
+    }
+
+    // o(nlogn)
+    public static void function3(long n) {
+        System.out.println("o(nlogn)算法");
+        long k = 0;
+        for (long i = 0; i < n; i++) {
+            for (long j = 1; j < n; j = j * 2) { // 注意这里j=1
+                k++;
+            }
+        }
+    }
+
+    public static void main(String[] args) {
+        while(true) {
+            Scanner in = new Scanner(System.in);
+            System.out.print("输入n: ");
+            int n = in.nextInt();
+            long startTime = System.currentTimeMillis();
+
+            function1(n);
+            // function2(n);
+            // function3(n);
+
+            long endTime = System.currentTimeMillis();
+            long costTime = endTime - startTime;
+            System.out.println("算法耗时 == " + costTime + "ms");
+        }
+    }
+}
 ```
 
 # 总结