基本Java程序：if语句？

Question

我制作的程序旨在根据两个问题产生关于“穿着/着装”的文字建议。外面目前的温度和天气情况如何？

将有3个范围：（< = 32）（33 - 55）（56+）华氏度 和4个选择为天气状况：晴朗，多云，下雨，下雪

使用下面我代码只有当我输入温度低于32°F时才能生成适当的建议。如果我为剩余的两个温度范围执行了相同的代码，我将如何生成推荐，就像冻结温度变量输入一样？

if (temperature <= 32){ 
      if (weatherCondition == 4){ 
       freezingSnowing(); 
      } 
      else if (weatherCondition == 3){ 
       freezingCloudy(); 
      } 
      else if (weatherCondition == 2){ 
       freezingRain(); 
      } 
      else { 
       freezingSunny(); 
     } 

      if ((temperature >= 33) && (temperature <= 60)){ 
      if (weatherCondition == 4){ 
       warmSnowing(); 
      } 
      else if (weatherCondition == 3){ 
       warmCloudy(); 
      } 
      else if (weatherCondition == 2){ 
       warmRain(); 
      } 
      else { 
       warmSunny(); 
     } 

     } 
     } 

//These are the recommendations that I would like to appear// 


public static void freezingSnowing()  
    { 
     JOptionPane.showMessageDialog(null, "It's is snowing! I recommend that you dress very warm" + 
          "and wear a large coat that is preferably water proof."); 
    } 

    // Temp <= 32 and weather condition = 3 // 
    public static void freezingCloudy() 
    { 
     JOptionPane.showMessageDialog(null, "Yikes it's below freezing, but at least it's just cloudy." + 
          " I would suggest that today you dress very warm and bring rain or snow gear just in case."); 
    } 

    // Temp <= 32 and weather condition = 2 // 
    public static void freezingRain() 
    { 
     JOptionPane.showMessageDialog(null, "Be careful freezing temperatures and rain is very dangerous!" + 
          " If however you will be venturing outside remeber to dress warm and be cautious of icy spots."); 
    } 

     // Temp <= 32 and weather condition = 1 // 
    public static void freezingSunny() 
    { 
     JOptionPane.showMessageDialog(null, "Looks may be decieving today. Don't forget to dress warm" + 
          " it looks nice and sunny out but it is still freezing."); 
    } 


    public static void warmSnowing() 
    { 
     JOptionPane.showMessageDialog(null, "It's is snowing, but based on the temperature it could turn to rain any minute! I recommend that you dress very warm" + 
          "and wear a large coat that is preferably water proof."); 
    } 

} 

Answer 1

您还没有关闭您的括号正确

if (temperature <= 32){ 
      if (weatherCondition == 4){ 
       freezingSnowing(); 
      } 
      else if (weatherCondition == 3){ 
       freezingCloudy(); 
      } 
      else if (weatherCondition == 2){ 
       freezingRain(); 
      } 
      else { 
       freezingSunny(); 
     } 

应该有一个更右括号别人后，只有这样，你就可以检查其他条件

if (temperature <= 32){ 
      if (weatherCondition == 4){ 
       freezingSnowing(); 
      } 
      else if (weatherCondition == 3){ 
       freezingCloudy(); 
      } 
      else if (weatherCondition == 2){ 
       freezingRain(); 
      } 
      else { 
       freezingSunny(); 
     } 
} 

if ((temperature >= 33) && (temperature <= 60)){ 
      if (weatherCondition == 4){ 
       warmSnowing(); 
      } 
      else if (weatherCondition == 3){ 
       warmCloudy(); 
      } 
      else if (weatherCondition == 2){ 
       warmRain(); 
      } 
      else { 
       warmSunny(); 
      }  
} 

Answer 2

适当地放入括号。这个代码块将被输入的唯一方式是如果temperature <= 32。另一种情况是不可能进入的。

if (temperature <= 32) { 
     if (weatherCondition == 4) { 
      freezingSnowing(); 
     } else if (weatherCondition == 3) { 
      freezingCloudy(); 
     } else if (weatherCondition == 2) { 
      freezingRain(); 
     } else { 
      freezingSunny(); 
     } 
    } else if ((temperature >= 33) && (temperature <= 60)) { 
     if (weatherCondition == 4) { 
      warmSnowing(); 
     } else if (weatherCondition == 3) { 
      warmCloudy(); 
     } else if (weatherCondition == 2) { 
      warmRain(); 
     } else { 
      warmSunny(); 
     } 

    } 

另外值得一提的是，您weatherCondition值是枚举一个很好的候选人，或使用switch声明。

Answer 3

为什么当你删除一些复杂的代码不工作变得更明显的原因：

if (temperature <= 32) 
{ //outer if begins 
    if (true) 
    { 
     freezingSunny(); 
    } 
    if ((temperature >= 33) && (temperature <= 60)) /* notice we are still inside the outer if */ 
    { //inner if begins 
     if (true) 
     { 
      warmSunny(); 
     } 
    } //inner if ends 
} //outer if ends 

现在我们可以看到，如果外，如果是真正的内部，如果只达到了 - 如果外层如果是真的，内层如果永远不会真的，所以这段代码永远不会运行。

Answer 4

您可以使用IF-ELSEIF-ELSE类，以避免混乱上}支架

if (temperature <= 32){ 
     if (weatherCondition == 4){ 
      freezingSnowing(); 
     } 
     else if (weatherCondition == 3){ 
      freezingCloudy(); 
     } 
     else if (weatherCondition == 2){ 
      freezingRain(); 
     } 
     else { 
      freezingSunny(); 
     } 
} 
    else if ((temperature >= 33) && (temperature <= 60)){ 
     if (weatherCondition == 4){ 
      warmSnowing(); 
     } 
     else if (weatherCondition == 3){ 
      warmCloudy(); 
     } 
     else if (weatherCondition == 2){ 
      warmRain(); 
     } 
     else { 
      warmSunny(); 
     } 
} 
else 
{ 
// 3rd range 
} 

Answer 5

您if...else..条件错过了右括号。在检查(33 - 55)范围之前应该已经关闭了if (temperature <= 32) {，并且由于<32范围已经处理，我们可以使用else if构造如else if (temperature <= 55)来测试它，并且最后的else可以处理>55条件。

而不是使用这么多if..else if构造用于测试weatherCondition我宁愿switch..case声明。

我将写像

if (temperature <= 32) { 
    switch (weatherCondition) { 
    case 4: 
     freezingSnowing(); 
     break; 
    case 3: 
     freezingSnowing(); 
     break; 
    case 2: 
     freezingSnowing(); 
     break; 
    default: 
     freezingSunny(); 
    } 
} else if (temperature <= 55) { 
    switch (weatherCondition) { 
    case 4: 
     warmSnowing(); 
     break; 
    case 3: 
     warmCloudy(); 
     break; 
    case 2: 
     warmRain(); 
     break; 
    default: 
     warmSunny(); 
    } 
} else { 
    // handle >=56 
}