编译时错误 - 在import java.io.BufferedReader中找不到符号;

问：

将 Java 与 NetBeans IDE 结合使用时，我有一个程序，在我编译它之前，它不会给我任何错误或警告，但随后它会告诉我：

error: cannot find symbol
import java.io.BufferedReader;
  symbol:   class BufferedReader
  location: package java.io
1 error

（底部有完整错误）

举个完整的例子，我将使用从我正在使用的插件 CODAPPS 生成的模板，我所做的只是添加行 .示例中未使用导入，但错误与我的程序相同：import java.io.BufferedReader;

StateMachine.java

/**
 * Your application code goes here
 */

package userclasses;
import java.io.BufferedReader;
import generated.StateMachineBase;
import com.codename1.ui.*; 
import com.codename1.ui.events.*;
import com.codename1.ui.util.Resources;

/**
 *
 * @author Your name here
 */
public class StateMachine extends StateMachineBase {
    public StateMachine(String resFile) {
        super(resFile);
        // do not modify, write code in initVars and initialize class members there,
        // the constructor might be invoked too late due to race conditions that might occur
    }

    /**
     * this method should be used to initialize variables instead of
     * the constructor/class scope to avoid race conditions
     */
    protected void initVars(Resources res) {
    }

}

错误：

Updating property file: C:\Users\hackr\Documents\NetBeansProjects\CodenameOne Hello World\build\built-jar.properties
Compile is forcing compliance to the supported API's/features for maximum device compatibility. This allows smaller
        code size and wider device support
Compiling 3 source files to C:\Users\hackr\Documents\NetBeansProjects\CodenameOne Hello World\build\tmp
C:\Users\hackr\Documents\NetBeansProjects\CodenameOne Hello World\src\userclasses\StateMachine.java:6: error: cannot find symbol
import java.io.BufferedReader;
  symbol:   class BufferedReader
  location: package java.io
1 error

编译程序的命令是，当我在 NetBeans 中单击绿色的“播放”按钮时生成的命令是：

ant -f "C:\\Users\\hackr\\Documents\\NetBeansProjects\\CodenameOne Hello World" -Dnb.internal.action.name=run run