java - 在 Java 中将 java.lang.object 转换为 int

Question

我有一个返回 java.lang.object 类型对象的方法，我想将它转换为 int。我试过这个:

oldComment.get("count"); 

返回一个 java.lang.object 并且我想将它转换为 int。我试过:

(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();

这是导致问题的代码 (Integer.parseInt(oldComment.get("likes").toString()))。

错误堆栈跟踪:

[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)

以上均无效。我如何转换它？

Answer 1

首先，你不应该返回java.util.Object，这是一个非常糟糕的习惯。如果你的值是一个数字，你应该返回 java.lang.Number。如果是字符串，则返回java.lang.String等

如果你没有选择，你可以用这个代码转换它:

// 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());
}

编辑:在您的堆栈跟踪中，您的程序尝试解析一个空字符串，因此它会抛出一个 NumberFormatException，您应该捕获它。