我是否正确使用了构造函数?打印出数据位置 (Java)

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。如果您可以查看并告诉我为什么当我尝试打印此数据时，它会显示(我假设是(数据位置。我想不出办法让它打印出名称、凝固点、沸点和单位数。也欢迎任何关于提高效率的建议。

这是头等舱

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);
    }

}

这是第二类。

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：

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

Answer 1

因为当前您正在打印对对象的引用。尝试这样的事情：

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

这应该为您提供对象内的数据。

此外，您可以重写 toString(( 方法并编写自己的实现。

像这样：

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

你的构造函数很好。这里实际上没有什么坏处。在java中，每个类都有一个默认的toString((方法，它可以打印出你在那里看到的内容。您可以免费获得它，但它的信息量不是很大。

尝试将其添加到您的化学类中：

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

并根据需要进行扩展。

Answer 3

你需要像这样重写 toString(( 方法：

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

您可以根据需要设置返回语句的格式。

您的构造函数没有问题，绝对没问题。