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Learning the Java Language
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Classes and Objects
Questions and Exercises: Objects
Questions
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What's wrong with the following program?
public class SomethingIsWrong {
public static void main(String[] args) {
Rectangle myRect;
myRect.width = 40;
myRect.height = 50;
System.out.println("myRect's area is " + myRect.area());
}
}
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The following code creates one array and one
string object.
How many references to those objects exist after the code executes?
Is either object eligible for garbage collection?
...
String[] students = new String[10];
String studentName = "Peter Parker";
students[0] = studentName;
studentName = null;
...
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How does a program destroy an object that it creates?
Exercises
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Fix the program called
SomethingIsWrong
shown in Question 1.
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Given the following class,
called
NumberHolder
, write some code that creates an instance of the class,
initializes its two member variables,
and then displays the value of each member variable.
public class NumberHolder {
public int anInt;
public float aFloat;
}
Check your answers.