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Subgoals

Section 4.16 ObjUse-WE7-P1: Aliasing

Subgoals for using objects (creating instances).

  1. Declare variable of appropriate class datatype.
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  2. Assign to variable: keyword new, followed by class name, followed by ().
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  3. Determine whether parameter(s) are appropriate (API)
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    1. Number of parameters
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    2. Data types of the parameters
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Subsection 4.16.1

Exercises Exercises

1.
Q20: What is the value of gamma after this code segment is run?
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Widget alpha = new Widget(5);
Widget beta = new Widget(15);
Widget delta = alpha;
delta.setBibs(25);
beta = delta;
beta.setBibs(30);

int gamma = alpha.getBibs();
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2.
Q21: What are the values of gamma and zeta after this code segment is run?
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Widget alpha = new Widget(0);
Widget beta = new Widget(24);
Widget delta = alpha;
delta.setBibs(40);
beta = delta;
beta.setBibs(30);
delta = new Widget(50);

int gamma = alpha.getBibs();
int zeta = delta.getBibs();
  • gamma = 0; zeta = 0;
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  • Incorrect
  • gamma = 24; zeta = 30;
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  • Incorrect
  • gamma = 30; zeta = 50;
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  • Correct
  • gamma = 40; zeta = 50;
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  • Incorrect
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3.
Q22: What is the value of gamma after this code segment is run?
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Widget alpha = new Widget(55);
Widget beta = new Widget(70);
alpha.setBibs(46); 
Widget delta = alpha;
beta.setBibs(79);
delta = new Widget(50);

int gamma = alpha.getBibs() + 10;
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