The Java Tutorials have been written for JDK 8. Examples and practices described in this page don't take advantage of improvements introduced in later releases and might use technology no longer available.
See Java Language Changes for a summary of updated language features in Java SE 9 and subsequent releases.
See JDK Release Notes for information about new features, enhancements, and removed or deprecated options for all JDK releases.
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()); } }
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; ...
How does a program destroy an object that it creates?
Fix the program called SomethingIsWrong
shown in Question 1.
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; }