Question

我需要一些帮助来弄清楚为什么这不起作用。是否可能只是嵌套的if-else语句或if-else语句的规则，通常只允许一个System.out.print语句？我需要输出＆＃34;可能有安全带。可能有防抱死制动器。＆＃34;

等等到2000年。

代码：

public class CarFeatures {
   public static void main (String [] args) {
      int carYear = 0;

      carYear = 1990;

      if (carYear <= 1969) {
         System.out.println("Probably has few safety features.");

      }else{
         if (carYear >= 1970) {
            System.out.println("Probably has seat belts.");

         }else{
            if (carYear >= 1990) {
               System.out.println("Probably has seat belts.");
               System.out.println("Probably has anti-lock brakes.");

         }else{
             if (carYear >= 2000) {
               System.out.println("Probably has seat belts.");
               System.out.println("Probably has anti-lock brakes.");
               System.out.println("Probably has air bags.");

             }
            }
         }
      }
      return;
   }
}

Answer 1

因为这个

 if (carYear >= 1970) {
        System.out.println("Probably has seat belts.");

     }else{

     }

1990年＆gt; 1970年，所以只需打印“可能有安全带。”

Answer 2

让if{...} else {...} else will not be entered into if the if`为真

删除它们

 if {
    ...
 }else{
     if (carYear >= 1970) {
        System.out.println("Probably has seat belts.");

     }
     if (carYear >= 1990) {
           System.out.println("Probably has seat belts.");
           System.out.println("Probably has anti-lock brakes.");

     }
      if (carYear >= 2000) {
           System.out.println("Probably has seat belts.");
           System.out.println("Probably has anti-lock brakes.");
           System.out.println("Probably has air bags.");

      }
 }

Answer 3

出现此问题是因为1990大于或等于1990，但它也大于或等于1970。因为1970语句首先出现在代码中，所以它永远不会到达1990语句。

要解决此问题，您的代码中可能会出现各种优化：

您可以在一行上声明{init} carYear 1990。
在嵌套级别使用if语句而不是else语句，不必复制print语句。

尝试以下代码here!

public class CarFeatures {
  public static void main (String [] args) {
    int carYear = 1990;

    if (carYear <= 1969) {
      System.out.println("Probably has few safety features.");
    } else {
      if (carYear >= 1970) {
        System.out.println("Probably has seat belts.");
      } 
      if (carYear >= 1990) {
        System.out.println("Probably has anti-lock brakes.");
      }
      if (carYear >= 2000) {
        System.out.println("Probably has air bags.");
      }
    }
  }
}

[Java]嵌套if else语句+多个System.out.print命令

3 个答案: