Question

这似乎是一个非常简单的问题，但我不确定我是否正确使用这些构造函数。如果你可以看看并告诉我为什么当我尝试打印这些数据时，它会显示（我假设是）数据位置。我无法想办法打印出名称，冰点，沸点和单位数量。任何有关提高效率的建议也是受欢迎的。

这是第一堂课

public class ChemicalInventory {

    public static void main(String[] args) {

    listInventory();
    }


    public static void listInventory(){
        Chemical Ethanol        = new Chemical("Ethanol",         "-173",   "172",   "1575");
        Chemical Oxygen         = new Chemical("Oxygen",          "-363",   "-306",  "1000");
        Chemical Water          = new Chemical("Water",           "32",     "212",   "5000");
        Chemical Benzene        = new Chemical("Benzene",         "41.9",   "176.2", "2750");
        Chemical EthyleneGlycol = new Chemical("Ethylene Glycol", "8.78",   "378",   "1900");

        System.out.println("Current Chemical Inventory: ");
        System.out.println(Ethanol);
        System.out.println(Oxygen);
        System.out.println(Water);
        System.out.println(Benzene);
        System.out.println(EthyleneGlycol);
    }



}

这是第二节课。

public class Chemical {

    private String chemName;
    private String chemFreezingPoint;
    private String chemBoilingPoint;
    private String chemUnitNumbers;


    public Chemical(String name, String freezingPoint, String boilingPoint, String unitNumbers){
    chemName = name;
    chemFreezingPoint = freezingPoint;
    chemBoilingPoint = boilingPoint;
    chemUnitNumbers = unitNumbers;
    }


    //String[][] chemArray = new String [5][4];
    String[][] chemArray = {{"Ethanol","-173","172","1575"},{"Oxygen","-363","-306","1000"},{"Water","32","212","5000"},
                            {"Benzene","41.9","176.2","2750"},{"Ethylene Glycol","8.78","378","1900"}};

}

这是我运行程序时得到的结果：

Current Chemical Inventory: 
Chemical@15db9742
Chemical@6d06d69c
Chemical@7852e922
Chemical@4e25154f
Chemical@70dea4e

Answer 1

因为您当前正在打印对象的引用。尝试这样的事情：

        System.out.println(Ethanol.toString());

这应该为您提供Object内的数据。

此外，您可以覆盖toString（）方法并编写自己的实现。

这样的事情：

public class Chemical {

    private String chemName;
    private String chemFreezingPoint;
    private String chemBoilingPoint;
    private String chemUnitNumbers;


    public Chemical(String name, String freezingPoint, String boilingPoint, String unitNumbers){
    chemName = name;
    chemFreezingPoint = freezingPoint;
    chemBoilingPoint = boilingPoint;
    chemUnitNumbers = unitNumbers;
    }


    //String[][] chemArray = new String [5][4];
    String[][] chemArray = {{"Ethanol","-173","172","1575"},{"Oxygen","-363","-306","1000"},{"Water","32","212","5000"},
                            {"Benzene","41.9","176.2","2750"},{"Ethylene Glycol","8.78","378","1900"}};

     public String toString(){
        return // Return the string in the format you want here... 
     }

}

Answer 2

您需要覆盖toString（）方法，如下所示：

@Override
public String toString() {
    return "Chemical [chemName=" + chemName + ", chemFreezingPoint=" + chemFreezingPoint + ", chemBoilingPoint="
            + chemBoilingPoint + ", chemUnitNumbers=" + chemUnitNumbers + "]";
}

您可以随意格式化return语句。

你的构造函数没有问题，绝对没问题。

Answer 3

你的建造者很好。实际上这里什么都没有打破。在java中，每个类都有一个默认的toString（）方法，它打印出来，以及你在那里看到的内容。你可以免费获得，但它的信息量不大。

尝试将此添加到您的化学类：

public String toString(){
 return "I am a chemical:" + name;
}

并根据需要进行扩展。

我正确使用构造函数吗？打印出数据位置（Java）

3 个答案: