Chapter 4.How Objects Behave

Declearing and initializing instance variables

Instance variables always get a default value.If you don’t explicitly assign a value variable,the instance variable still has a value!

Type Value integers 0 floating points 0.0 booleans false references null

The difference between instance and local variables

• Instance variables are declared inside a class but not with a method.
• Local variables are declared within a method.

Comparing variables(primitives or references)

• To copare two primitives ,use the == operator
• You want to know if two reference variables refer to a single obeject on the heap,using the == operator
• You want to know if two object are equal.You need the .equal() method.

声明和初始化实例变量

实例变量有一个缺省的值。如果你没有明确指定变量的值，实例变量会保持那个缺省的值

类型 值 integers 0 floating points 0.0 booleans false references null

实例变量和局部变量的区别

• 实例变量被声明在类里而不是方法里
• 局部变量被声明在方法里

比较基本变量与引用变量

• 两个基本变量的比较试用 == 操作符
• 你想知道两个引用变量是否指向同一个对象，使用 == 操作符
• 你想知道两个对象是否相等，使用 .equal()方法