java lang NumberFormatException For input string undefine

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在将字符串转换为数字时导致此错误，解决此问题的思路：1、添加Try catch语句，2、判断字符串是否为数字，将介绍java中判断字符串是否为数字的方法的几种方法。

完整错误信息：

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java.lang.NumberFormatException: For input string: "undefined"    at java.lang.NumberFormatException.forInputString(Unknown Source)    at java.lang.Integer.parseInt(Unknown Source)    at java.lang.Integer.valueOf(Unknown Source)    at com.xinghe.frame.base.web.BaseSpringController.getInteger(BaseSpringController.java:123)    at com.xinghe.edu.web.BaseAdminController.setFieldValues(BaseAdminController.java:340)    at com.xinghe.platform.action.ResResourcePublic.saveComment(ResResourcePublic.java:504)    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)    at java.lang.reflect.Method.invoke(Unknown Source)    at org.springframework.web.bind.annotation.support.HandlerMethodInvoker.invokeHandlerMethod(HandlerMethodInvoker.java:177)    at org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.invokeHandlerMethod(AnnotationMethodHandlerAdapter.java:446)    at org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.handle(AnnotationMethodHandlerAdapter.java:434)    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:943)    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:877)    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:966)    at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:868)    at javax.servlet.http.HttpServlet.service(HttpServlet.java:648)    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:842)    at javax.servlet.http.HttpServlet.service(HttpServlet.java:729)    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:291)    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239)    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)    at com.auth.filter.AuthorizationFilter.doFilterInternal(AuthorizationFilter.java:77)    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)    at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:344)    at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:261)    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239)    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)    at com.auth.filter.AuthenticationFilter.doFilterInternal(AuthenticationFilter.java:115)    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)    at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:344)    at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:261)    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239)    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)    at com.xinghe.activate.filter.ActivateFilter.doFilterInternal(ActivateFilter.java:52)    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)    at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:344)    at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:261)    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239)    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)    at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:88)    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239)    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:219)    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:106)    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502)    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:142)    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79)    at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:617)    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88)    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:518)    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1091)    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:668)    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1521)    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1478)    at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)    at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)    at java.lang.Thread.run(Unknown Source)
  
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发生错误的底层代码:

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java.lang.NumberFormatException.forInputString(Unknown Source)    at java.lang.Integer.parseInt(Unknown Source)    at java.lang.Integer.valueOf(Unknown Source)
  
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发生错误原因：

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由于AJAX调用的时候对应的参数未设置，导致后台获取到的是字符串”undefined”，在将它转换成Integer类型的时候出的错。

解决办法：

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AJAX调用的时候设置对应的参数；
添加Try catch语句；
最好的做法还是应该在进行参数类型转换的时候先对待转换的值做一下检测，看是否符合目标类型格式；

java中判断字符串是否为数字的方法的几种方法

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1.用JAVA自带的函数

public static boolean isNumeric(String str){  for (int i = 0; i < str.length(); i++){   System.out.println(str.charAt(i));   if (!Character.isDigit(str.charAt(i))){    return false;   }  }  return true; }
  
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2.用正则表达式

首先要import java.util.regex.Pattern 和 java.util.regex.Matcher

public boolean isNumeric(String str){    Pattern pattern = Pattern.compile("[0-9]*");    Matcher isNum = pattern.matcher(str);   if( !isNum.matches() ){       return false;    }    return true; }
  
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3.使用org.apache.commons.lang

org.apache.commons.lang.StringUtils;
boolean isNunicodeDigits=StringUtils.isNumeric(“aaa123456789”);
http://jakarta.apache.org/commons/lang/api-release/index.html下面的解释:isNumeric

public static boolean isNumeric(String str)Checks if the String contains only unicode digits. A decimal point is not a unicode digit and returns false.null will return false. An empty String ("") will return true. StringUtils.isNumeric(null)   = false StringUtils.isNumeric("")     = true StringUtils.isNumeric("  ")   = false StringUtils.isNumeric("123")  = true StringUtils.isNumeric("12 3") = false StringUtils.isNumeric("ab2c") = false StringUtils.isNumeric("12-3") = false StringUtils.isNumeric("12.3") = falseParameters:str - the String to check, may be null Returns:true if only contains digits, and is non-null
  
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几种实现方式比较

上面三种方式中，第二种方式比较灵活。

第一、三种方式只能校验不含负号“-”的数字，即输入一个负数-199，输出结果将是false；

而第二方式则可以通过修改正则表达式实现校验负数，将正则表达式修改为“^-?[0-9]+”即可，修改为“-?[0-9]+.?[0-9]+”即可匹配所有数字。

           

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