Question

在调用变量时，我很难找到java正在遇到什么问题。我正在创建一个简单的聊天机器人，这是我到目前为止所做的：

public class Chatbot {
    public static void main(String[] args) {
        String name = JOptionPane.showInputDialog("Hi! How are you? My name is Chatbot! What is yours? ");
        if (name.compareTo("a")<0){
            String city = JOptionPane.showInputDialog("Nice to meet you! Where are you from, "+name);
        }
        else
        {
            String city = JOptionPane.showInputDialog("Huh. That's a strange name. Where are you from,"+name);  
        }


        if (!city.equals("Seattle")){

        }

    }
}

我的问题是java不会在if else语句中识别变量city，所以说city不能解析。如何让java识别布尔表达式中的对象？我做错了什么？

Answer 1

目前city的范围仅限于if或else block。通过在方法级别声明它来使其成为局部变量来增加其范围。

public static void main（String [] args）{

String name = JOptionPane.showInputDialog("Hi! How are you? My name is Chatbot! What is yours? ");
String city="";
if (name.compareTo("a")<0){
    city = JOptionPane.showInputDialog("Nice to meet you! Where are you from, "+name);
}
else
    {
    city = JOptionPane.showInputDialog("Huh. That's a strange name. Where are you from,"+name);  
     }

Answer 2

Decalre String city = null位于顶部。然后使用它。它必须超出if else块。

String city=null;
    String name = JOptionPane.showInputDialog("Hi! How are you? My name is Chatbot! What is yours? ");
if (name.compareTo("a")<0){
            city = JOptionPane.showInputDialog("Nice to meet you! Where are you from, "+name);
        }
        else
        {
            city = JOptionPane.showInputDialog("Huh. That's a strange name. Where are you from,"+name);  
        }

Answer 3

如前所述，您需要在if-else块之外声明city，如下所示：

public static void main(String[] args) {
    String name = JOptionPane.showInputDialog("Hi! How are you? My name is Chatbot! What is yours?");
    String city = null;
    if (name.compareTo("a")<0){
       city = JOptionPane.showInputDialog("Nice to meet you! Where are you from, "+name);
    }
        else
    {
        city = JOptionPane.showInputDialog("Huh. That's a strange name. Where are you from,"+name);  
    }
    if (!city.equals("Seattle")){

    }

}

Answer 4

尝试追随希望它有所帮助。

 public static void main( String[] args )
        {

            String name = JOptionPane.showInputDialog( "Hi! How are you? My name is Chatbot! What is yours? " );
            String city = "";
            if ( name.compareTo( "a" ) < 0 )
            {

                city = JOptionPane.showInputDialog( "Nice to meet you! Where are you from, " + name );
            }
            else
            {
                city = JOptionPane.showInputDialog( "Huh. That's a strange name. Where are you from," + name );
            }

            if ( !city.equals( "Seattle" ) )
            {

            }

        }

不会从布尔表达式中调用变量

4 个答案: