s1 change to s2

Author: Xunzhuo

notes/Java 基础.md

@@ -233,7 +233,7 @@ String s1 = new String("aaa");
 String s2 = new String("aaa");
 System.out.println(s1 == s2);           // false
 String s3 = s1.intern();
-String s4 = s1.intern();
+String s4 = s2.intern();
 System.out.println(s3 == s4);           // true
 ```