java - 收到 'else'，但没有 'if' 错误

Question

import javax.swing.JOptionPane;

public class Cortana2 {

    public static void main(String[] args) throws Exception {
        //Declaring Variables (Add more commands) 
        String command;
        // Command will always stay the same
        // All strings below are commands to put in
        String Steam;
        String League;
        League=("League"); 
        Steam=("Steam");  
        command= JOptionPane.showInputDialog("Give a valid command");

        if (command == null) {  
            JOptionPane.showMessageDialog(null, "This is not a valid command. If you have forgotten what commands are valid, please refer to Devon for assistance");
            JOptionPane.getRootFrame().dispose();
        } else if (command == League) {
            Runtime.getRuntime().exec("\"D:/LeagueClient.exe\"");
        } else if (command == Steam) { 
            Runtime.getRuntime().exec("\"C:/Program Files (x86)/Steam/Steam.exe\"");    
        }
    }
}

不能 100% 确定为什么会出现错误。我看到其他人说要从“if”语句中删除分号，但当我运行程序并输入命令时，什么也不会执行。抱歉，如果有任何内容格式不正确。

Answer 1

if (command == null);

不要加“;”在 if/else 语句的末尾。

but then nothing executes when I run the program and type in commands

不要使用 == 来比较字符串。

改用String.equals(...)方法

此外，变量名称不应以大写字符开头。