Rec 01

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Problems

01. Information Hiding and Tell, Don't Ask

This is a typical question about infromation hiding and "Tell, Don't Ask". Nothing much to talk about.

02. Stack and Heap

The thing we should learn from this question is how to declare and initialize an array in Java

// Declaration
private double[] coord2D;

// Initialization
coord2D = new double[] {1，2}；

03. Method Invocation

1. We cannot change the CTT of a variable. So, if we have declared Circle c, we cannot use String c anymore in the same segement.

2. Always pay attention to whether the Object::equals(Object) has been overriden or not. If not, it will always compare whether two instances are the same or not.

Tips

1. We cannot change the CTT of a variable. So, if we have declared Circle c, we cannot use String c anymore in the same segement.

2. Always pay attention to whether the Object::equals(Object) has been overriden or not. If not, it will always compare whether two instances are the same or not.