Java Relationship Questions

[Zemi25]

1.What is an "is a" relationship? How does it apply to the world of objects?
2. What is a "has a" relationship?
3. Explain how parent and child classes are related to base and derived classes.
5. Explain the modifiers public, protected and private.

[mohan_java]

hi actaully i want to know that " how to call the garbage collector in java"
instead of using system.gc().
bcz if we use that may be or mayn't the jvm will call the GC, but i want to call the GC manually.

plz send me the resplonse

[rachilc]

Zemi,

1.what is an "is a" relationship? how does it apply to the world of objects?

when a class inherits from another class, the former is a specific form of the latter. Example, if dog inherits from animal, we can say dog is a animal.

2. What is a "has a" relationship?

whenever one object has a member varibale that is a reference to another object. It is a has a relationship.
For example

class dog { tail dogtail; //here tail is another object }

now we can say a dog has a tail.

3. Explain how parent and child classes are related to base and derived classes.
parent = base class
child = derived class.
I guess it's just terminology

5. Explain the modifiers public, protected and private.
public : all instances of other classes, irrespective of the module, namespace or package can have access to this artifact (class, method, variable)

protected : all instances of other classes in the same package and subclasses in other packages can have acces to this (once child class inherits a protected method or variable, it becomes private with respect to child class). This cannot be applied to top level classes in java.

Private : only, i repeat, only memebrs of the same class can access this. Nobody from outside, even if from same package can access this.

Hope this helps.

[rachilc]

For Mohan,

Try not to cross post. Your topic will have more visibilty if it has it's own subject in a separate thread.

Anyway, I am not the moderator, so here goes:

IMHO, you CANNOT guarantee the garbage collecter will run, no matter what method you use.

Two ways to recommend running the garbage collecter are:

System.gc() as you already pointed out.

Runtime rt = Runtime.getRuntime();

rt.gc();

Both serve the same purpose and do not force garbage collecter to run.

[bhaskar22]

please find the some important questions for Core Java and HR interviews.

[dipak2704]

What is String.intern()?

[anveth]

str.intern() is used to convert normal string class to canonical class

String s=new String("string");
String s1=s.intern();

[vinodkrmenaria]

we can call garbage collector in java in two ways:
1)System.gc
2)RunTime.gc

[sagar salunkhe]

hi actaully i want to know that " how to call the garbage collector in java"
instead of using system.gc().
bcz if we use that may be or mayn't the jvm will call the GC, but i want to call the GC manually.

plz send me the resplonse

hey mohan actually u can use an alternate method to run gc explicitly.
just use following code.
"Runtime rt = Runtime.getRuntime();
rt.gc(); "