HashMapTest.java uses unchecked or unsafe operations.

Hi

I am new to Java. m using HashMap class.
when i compile "javac HashMapTest.java", i get following error:
Note: HashMapTest.java uses unchecked or unsafe operations.
Note: Recompile with -Xlint:unchecked for details.

I was using:
HashMap h= new HashMap();

I made some changes in my code
import java.util.*;
public class HashMapTest {
public static void main(String[] args) {
// creating HashMap object
HashMap<String,Object> h= new HashMap<String,Object>();
// creating Student objects
Student s1 = new Student ("ali" , 1);
// adding elements (Student objects) where roll nos
// are stored as keys and student objects as values
h.put("one", s1);
............
........
.....

Now, after compile, there is no error but when i run my code then there is following exception:
Exception in thread "main" java.lang.UnsupportedClassVersionError: HashMapTest
(Unsupported major.minor version 49.0)
at java.lang.ClassLoader.defineClass0(Native Method)
at java.lang.ClassLoader.defineClass(Unknown Source)
at java.security.SecureClassLoader.defineClass(Unknow n Source)
at java.net.URLClassLoader.defineClass(Unknown Source)
at java.net.URLClassLoader.access$100(Unknown Source)
at java.net.URLClassLoader$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClassInternal(Unknown Source)


Please guide me to resolve this error
Cheers

What ArrayListTest class doing there in your application?

working fine in my system:

where is ArrayListTest class

Yep, he has something wrong with that class. Seems to he used some class libraries which are not supported with currently working version.

Sorry, that is HashMapTest

Oh man, you have edited the compilation error :p

In that case, your code is ok. Except that you work out correctly on the Student object. Constructor parameters...

My Student class looks fine, following is the code:

public class Student {
private String name;
private int rollNo;
// Standard Setters
public void setName (String name) {
this.name = name;
}
// Note the masking of class level variable rollNo
public void setRollNo (int rollNo) {
if (rollNo > 0) {
this.rollNo = rollNo;
}else {
this.rollNo = 100;
}
}
// Standard Getters
public String getName ( ) {
return name;
}
public int getRollNo ( ) {
return rollNo;
}
// Default Constructor
public Student() {
name = "not set";
rollNo = 100;
}
// parameterized Constructor for a new student
public Student(String name, int rollNo) {
setName(name); //call to setter of name
setRollNo(rollNo); //call to setter of rollNo
}
// Copy Constructor for a new student
public Student(Student s) {
name = s.name;
rollNo = s.rollNo;
}
// method used to display method on console
public void print () {
System.out.print("Student name: " +name);
System.out.println(", roll no: " +rollNo);
}
} // end of class

Everything working fine for me. Which Java version you used?

set

JAVA_HOME to the directory having latest JDK version

also
in your path variable replace all occurence of older path to new one.


one more thing, what do it return
java - version

Rakesh, you talking to me. If so, now it's useless, because all the things perfect for any version. :)

Sorry! i replied to jeer :(

i guess he compiled with 1.5 version and running with 1.4 :eek:

I have installed jdk1.5.0_14.
I have already included "C:\Program Files\Java\jdk1.5.0_14\bin;" in path environment variable.
how can i set JAVA_HOME?

I thought it's for me. :)

What the point with 1.4 Rakesh. Only the HashMap he used in advanced. But it support from 1.2. So...;)

i don't think JAVA code compiled with 1.5 will run using 1.4 version ( for all cases ) may be i am wrong. :confused:

if he have used some methods which were only in 1.5 , and not in 1.4 in that case it should certainly not run :confused:

Quote:

---

Originally Posted by rjuyal

i don't think JAVA code compiled with 1.5 will run using 1.4 version ( for all cases ) may be i am wrong. :confused:

---

You are 100% correct. May be confused with my last replay. What I try to say is this.

Some functions(libraries and so..) on later versions are not supported in newer versions. Basically Suns' deprecate them newer versions in different way. Only such thing I can see from our original code is the HashMap, supported from 1.2 and I think my numbers are correct. :)

HashMap<String,Object> h

this feature was not in 1.4 :cool:
in 1.4 we have to write:

HashMap h


BTW, i don't remember what do we say this feature <String,Object>

we call it Generics ;)

I am compiling and running my code using same java version. if i use
HashMap h
then there following error:
Note: HashMapTest.java uses unchecked or unsafe operations.
Note: Recompile with -Xlint:unchecked for details.

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