Convert java.lang.object to int in Java

Question

I have a method which returns a object of type java.lang.object and I want to convert it to int. I tried this:

oldComment.get("count");

return a java.lang.object and I want to convert it to int. I tried:

(Integer)oldComment.get("count");
Integer.valueOf(oldComment.get("count"));
Integer.parseInt(oldComment.get("count"));


con = Base.connection();
String query = "UPDATE COMMENT SET LIKES = ? WHERE POST_ID = ?";
PreparedStatement pst = con.prepareStatement(query);
pst.setObject(1, (Integer.parseInt(oldComment.get("likes").toString())) + Integer.valueOf(rateComment.getCount()));
pst.setString(2, rateComment.getPost_id());
int k = pst.executeUpdate();

This is the code (Integer.parseInt(oldComment.get("likes").toString())) that is causing issue.

Error Stacktrace:

[qtp25844331-17] ERROR spark.http.matching.GeneralError -
java.lang.NumberFormatException: For input string: ""
        at java.lang.NumberFormatException.forInputString(NumberFormatException.java:65)
        at java.lang.Integer.parseInt(Integer.java:592)
        at java.lang.Integer.parseInt(Integer.java:615)
        at com.soul.seeker.serviceImpl.CommentRatingServiceImpl.rateComment(CommentRatingServiceImpl.java:50)
        at com.soul.seeker.Application.lambda$main$12(Application.java:161)
        at spark.ResponseTransformerRouteImpl$1.handle(ResponseTransformerRouteImpl.java:47)
        at spark.http.matching.Routes.execute(Routes.java:61)
        at spark.http.matching.MatcherFilter.doFilter(MatcherFilter.java:130)
        at spark.embeddedserver.jetty.JettyHandler.doHandle(JettyHandler.java:50)
        at org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:189)
        at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:141)
        at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:119)
        at org.eclipse.jetty.server.Server.handle(Server.java:517)
        at org.eclipse.jetty.server.HttpChannel.handle(HttpChannel.java:308)
        at org.eclipse.jetty.server.HttpConnection.onFillable(HttpConnection.java:242)
        at org.eclipse.jetty.io.AbstractConnection$ReadCallback.succeeded(AbstractConnection.java:261)
        at org.eclipse.jetty.io.FillInterest.fillable(FillInterest.java:95)
        at org.eclipse.jetty.io.SelectChannelEndPoint$2.run(SelectChannelEndPoint.java:75)
        at org.eclipse.jetty.util.thread.strategy.ExecuteProduceConsume.produceAndRun(ExecuteProduceConsume.java:213)
        at org.eclipse.jetty.util.thread.strategy.ExecuteProduceConsume.run(ExecuteProduceConsume.java:147)
        at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:654)
        at org.eclipse.jetty.util.thread.QueuedThreadPool$3.run(QueuedThreadPool.java:572)
        at java.lang.Thread.run(Thread.java:745)

None of the above worked. How do I convert it?

What kind of object is it? What result do you expect if it is any kind of object? Suppose the object is an Apple, or a House, or whatever, then want integer value would you expect? — Jesper
– Jesper, Commented Mar 30, 2017 at 12:51
Please provide an example of one of your objects, and which Integer it should give, and why . — Arnaud
– Arnaud, Commented Mar 30, 2017 at 12:55

Dorian · Accepted Answer · 2017-03-30 13:05:52Z

2

First of all, you shouldn't return java.util.Object, it's a very bad habit. If your value it's a Numeric, you should return java.lang.Number. If it's a String, you should return java.lang.String, etc.

If you don't have choice, you can convert it with this code :

// This method can throw NumberFormatException, catch it if you want
public Integer toInt(Object obj) {
    // Use intValue on a Number to improve performance
    if(obj instanceof Number) {
         return ((Number) obj).intValue();
    }

    return Integer.parseInt(obj.toString());
}

EDIT : In your stacktrace, your program try to parse an empty String so it throws an NumberFormatException, you should catch it.

edited Mar 30, 2017 at 13:05

answered Mar 30, 2017 at 13:01

Dorian

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7 Comments

kittu Over a year ago

Its a method from other lib is returning. I don't have a choice but to try and convert it

Dorian Over a year ago

Ok so you can use my method or just only a Integer.parseInt(myObj) but you should catch the NumberFormatException to manage the empty String (maybe return 0 in this case ?)

kittu Over a year ago

your method is similar is this line right? (Integer.parseInt(oldComment.get("likes").toString()))

kittu Over a year ago

I am not sure why it is throwing NFE when there is a value inside it

Dorian Over a year ago

Yes the result is the same. In your stacktrace, the is no value : java.lang.NumberFormatException: For input string: ""

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