diff --git a/javaSE-day01/src/com/inmind/system05/Demo21.java b/javaSE-day01/src/com/inmind/system05/Demo21.java
index 2234a0c..027e246 100644
--- a/javaSE-day01/src/com/inmind/system05/Demo21.java
+++ b/javaSE-day01/src/com/inmind/system05/Demo21.java
@@ -1,5 +1,8 @@
 package com.inmind.system05;
 
+import java.net.SocketTimeoutException;
+import java.time.Duration;
+import java.time.Instant;
 import java.util.Date;
 
 /*
@@ -24,9 +27,21 @@ public class Demo21 {
 
         long end = System.currentTimeMillis();
         System.out.println("1000遍打印消耗的时间："+(end - begin));//毫秒级别
-
+        System.out.println("-----------------------------------");
         //我想要纳秒级别的时间差，怎么办？Instant
         //如何获取2个Instant的纳秒间隔呢？Duration
 
+        Instant b = Instant.now();
+
+        for (int i = 0; i < 1000; i++) {
+            System.out.println(i);
+        }
+        Instant e = Instant.now();
+//        System.out.println(e.getNano() - b.getNano());
+        //使用时间间隔，计算时间差
+        /*Duration duration = Duration.between(b, e);
+        System.out.println(duration.toNanos());*/
+        System.out.println(Duration.between(b,e).toNanos());
+        System.out.println(Duration.between(b,e).toMillis());
     }
 }