[Java] 7 images

1 Immutable String

String s = "abcd";
s = s.concat("ef");

2 equals() and hashCode():

if 2 objects equal : hashCode() equal, too
if hashCode() equal : the 2 object may be equal

3 Java Exception :
4 Collections

5 Java Aliasing 别名
,means one object can have different references


6 Heap and stack :

7 JVM