The problem is your runtime classpath. There's no magic with this error. It quite simply means that org.json.JSONException is not on your runtime classpath. Find the jar that has this class in it and put it on your runtime classpath.

Note that the jars / classes needed for runtime are not necessarily the same as those needed for compiling. You quite often need more on your runtime classpath than your compile classpath. If JSONException isn't used explicitly in the code you are compiling, then it won't have to be on your compile classpath. However, if one of the dependencies to your code needs JSONException and it's not on your runtime classpath, you will get a NoClassDefFoundError.

One other issue that can possibly occur is that you have 2 different versions of the json jar on your classpath. Usually the first version of the class on the classpath gets loaded and the other ignored. If the first jar didn't have the version / signature of JSONException you needed in it but the second did, the correct class you would still get ignored, since it was further down on the classpath.

That looks like a runtime error, not a compile error, so the build path probably doesn't help you. Do you have those jars in your classpath? That's what's used at runtime to find classes.

Add json jar to your classpath

or use java -classpath json.jar ClassName

Or add this to your maven pom.xml depedencies:

<dependency>
    <groupId>org.json</groupId>
    <artifactId>json</artifactId>
    <version>20090211</version>
</dependency>

Have you considered using Maven? for instance, if you wanted a JAR to pars JSON you could just include...

http://mvnrepository.com/artifact/org.codehaus.jackson/jackson-core-asl/1.9.6

<dependency>
    <groupId>org.codehaus.jackson</groupId>
    <artifactId>jackson-core-asl</artifactId>
    <version>1.9.6</version>
</dependency>

in a pom.xml, this will give you the jar for JSON.

Or better yet, use the org.json one...

http://mvnrepository.com/artifact/org.json/json

<dependency>
    <groupId>org.json</groupId>
    <artifactId>json</artifactId>
    <version>20090211</version>
</dependency>

Yes, you need to catch the exception.

But when you catch it, you should not just throw it on the floor. Your application needs to do something about the exception. Or if you / it is not expecting an exception to occur at runtime, then at least you should report it. Here's a minimal example (for an Android app)

try {
    ...
    JSONObject jObj = new JSONObject(stringaRis);
    ...
} catch (JSONException e) {
    Log.e("MYAPP", "unexpected JSON exception", e);
    // Do something to recover ... or kill the app.
}

Of course, this does not solve your problem. The next thing you need to do is to figure out why you are getting the exception. Start by reading the exception message that you have logged to logcat.

Re this exception message:

org.json.JSONException: Value A of type java.lang.String cannot be converted to JSONObject

I assume it is thrown by this line:

    JSONObject jObj = new JSONObject(stringaRis);

I think that it is telling you is that stringaRis has the value "A" ... and that cannot be parsed as a JSON object. It isn't JSON at all.

Its JSONObject not JsonObject.

Same goes for the parser, it's JSONParser not JsonParser.

JSON is always uppercase.