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Question

As soon as i think i get it, one or 2 paragraphs later i'm stuck again; so let me know, please, if i'm right in saying the following:
Student newonthis = puzzled;
here i go:
the object reference NEWONTHIS is an object of STUDENT type [the var newonthis contains a reference to an obj of type Student] which (obj) contains the value PUZZLED.
=============
Now another question,pls:
(from B Eckel's book Thinking in java)
//: c03:EqualsMethod2.java
// From 'Thinking in Java, 3rd ed.' (c) Bruce Eckel 2002
// www.BruceEckel.com. See copyright notice in CopyRight.txt.
import com.bruceeckel.simpletest.*;
class Value {
  int i;
public class EqualsMethod2 {
  static Test monitor = new Test();
  public static void main(String[] args) {
    Value v1 = new Value();
    Value v2 = new Value();
    v1.i = v2.i = 100;
    System.out.println(v1.equals(v2));
    monitor.expect(new String[] {
      "false"
} ///:~The output is FALSE because we are comparing primitives (integers) and not object values, right?
thanks in advance

Answer 1

Student newonthis = puzzled;
here i go:
the object reference NEWONTHIS is an object of STUDENT
type [the var newonthis contains a reference to an obj
of type Student]Correct up to here.
which (obj) contains the value
PUZZLED.No. That newon=puz assignment just assigns newon to point to the same Student object that puz is already pointing to. It is not the case that the object has the value puzzled. An object's "value" (which term isn't really standard, AFAIK) has nothing to do with which referenc(es) are pointing at it.
=============
Now another question,pls:
(from B Eckel's book Thinking in java)
//: c03:EqualsMethod2.java
// From 'Thinking in Java, 3rd ed.' (c) Bruce Eckel
2002
// www.BruceEckel.com. See copyright notice in
CopyRight.txt.
import com.bruceeckel.simpletest.*;
class Value {
int i;
public class EqualsMethod2 {
static Test monitor = new Test();
public static void main(String[] args) {
Value v1 = new Value();
Value v2 = new Value();
v1.i = v2.i = 100;
System.out.println(v1.equals(v2));
monitor.expect(new String[] {
"false"
} ///:~The output is FALSE because we are comparing
primitives (integers) and not object values, right?It's false because you're invoking the equals method which appears not to have been overriden. If you don't override equals, you'll get Object's equals method, which just compares references, so v1.equals(v2) in that case is the same as v1==v2. That comparison is false becuase v1 and v2 refer to two different objects. If you override equals to check the value of field i, it will return true.
Here's a chapter from Bloch's book that covers overriding equals and hashCode. You shold find more in any decent tutorial or text.
http://developer.java.sun.com/developer/Books/effectivejava/Chapter3.pdf