如何防止更改setter方法中的参数？

Question

例如，我有以下代码：

public class Weather {
    private int temperature;

    //Set temperature to t.
    //If t goes below -15, temperature should become -15.
    //If t goes above 40, temperature should become 40.
    //If t is already between -15 and 40, it should not be changed.
    public void setTemperature(int t){
        if(t>= -15 && t<= 40){
            temperature = t;
        }
        else if(t< -15){
            temperature = -15;
        }
        else if(t> 40){
            temperature = 40;
        }
    }
}

我的问题是，如果说有一个写信的客户

Weather temp1 = new Weather();
temp1.setTemperature(-20);
temp1.setTemperature(10);

然后将温度实际设置为10而不是-15，因为setTemperature函数被调用了两次。 如果温度已经设置为-15至40之间的值，我需要我的代码忽略以后对setter函数的任何调用。我该怎么做？ 上面的代码是我目前所拥有的。

Answer 1

尝试使用具有可为空状态的Integer代替：

private Integer temperature = null;

public void setTemperature(int t){
    if( temperature != null ) return;

    if(t>= -15 && t<= 40){
      temperature = t;
     }
     else if(t< -15){
      temperature = -15;
     }
     else if(t> 40){
      temperature = 40;
     }
    }
   }

Answer 2

使用Integer.MAX_VALUE初始化temperature ，并且如果setTemperature的值小于该值，则不要在setTemperature内部执行任何操作：

public class TestMan {
    public class Weather {
    private int temperature = Integer.MAX_VALUE;

    //Set temperature to t.
    //If t goes below -15, temperature should become -15.
    //If t goes above 40, temperature should become 40.
    //If t is already between -15 and 40, it should not be changed.
    public void setTemperature(int t){
        if (temperature < Integer.MAX_VALUE) return;
        if(t>= -15 && t<= 40){
            temperature = t;
        }
        else if(t< -15){
            temperature = -15;
        }
        else if(t> 40){
            temperature = 40;
        }
    }
}

Answer 3

根据您的要求：

如果温度已设置为-15至40之间的值，则我需要我的代码来忽略以后对setter函数的任何调用。

您可以使用一个标志来确定之前是否已经调用过setter，如果是，则请检查先前的temperature是否在您的范围内，或者是否像下面的代码所示：

public class Weather {
private int temperature;
private boolean sette_called = false;
//Set temperature to t.
//If t goes below -15, temperature should become -15.
//If t goes above 40, temperature should become 40.
//If t is already between -15 and 40, it should not be changed.
public void setTemperature(int t){
    if (sette_called)
    {
        if (temperature >= -15 && temperature <= 40)
             return;
    }
    if(t>= -15 && t<= 40){
        temperature = t;
    }
    else if(t< -15){
        temperature = -15;
    }
    else if(t> 40){
        temperature = 40;
    }
    sette_called = true;
}
}

Answer 4

尝试标记关键字是否正确。.我永远不会设置任何未来温度{

        private int temperature;
        bool flag = false;

        //Set temperature to t.
        //If t goes below -15, temperature should become -15.
        //If t goes above 40, temperature should become 40.
        //If t is already between -15 and 40, it should not be changed.
        public int setTemperature(int t)
        {
            if (flag == false)
            {
                if (t >= -15 && t <= 40)
                {
                    temperature = t;
                    flag = true;
                }
                else if (t < -15)
                {
                    temperature = -15;
                    flag = true;
                }
                else if (t > 40)
                {
                    temperature = 40;
                    flag = true;
                }
                return temperature;
            }
            else
            {
                return temperature;
            }
        }

Answer 5

使用整数数据类型。 设置temperature = null 。

private Integer temperature = null;

public void setTemperature(int t){
    if( temperature != null) {
        return;
    }

    if(t>= -15 && t<= 40){
      temperature = t;
    } else if(t< -15){
      temperature = -15;
    } else if(t> 40){
      temperature = 40;
    }
 }