java - 如何编写一个方法来确定数组中的最大值

Question

该数组是名为 CO2Data 的类的一部分，因此该数组是 CO2Data 数组。问题是我试图找到数组中的最大值，但我的方法不起作用。要从数组中获取值，该方法必须首先从 CO2data 类中获取它们。那么我的方法有什么问题:

    public static CO2Data highest (CO2Data []  arr2){
Scanner sc = null;
CO2Data highestindex = arr2[0].getTotalCO2;
for (int i = 0; i<arr2.length; i++){
arr2[i].getTotalCO2(sc.nextDouble());
if(arr2[i].getTotalCO2() > highestindex ) {
    highestindex = arr2[i].getTotalCO2();
}
}
System.out.println(highestindex);
return highestindex;
}

这是 CO2data 类的样子:

公共(public)类 CO2Data {

private String country; //A private variable will prevent other users from accessng and chaning these variables. 
private double totalCO2;
private double roadCO2;
private double CO2PerPerson;
private int carsPerPerson;

public CO2Data() { 
    country = "";//this sets the initial values for the different variables
    totalCO2 = 0;
    roadCO2 = 0;
    CO2PerPerson = 0;
    carsPerPerson = 0;
}

public String getCountry() {
    return country;
}

public void setCountry(String country) { //to set the country you have to use the this command to access the private variable
    this.country = country; //you have to use this.country instead of just country because the string county has been declared as a private variable. 
}

public double getTotalCO2() {
    return totalCO2;
}

    public void setTotalCO2(double totalCO2) {
        this.totalCO2 = totalCO2; //The this.item command allows you to access private variables. 
    }

    public double getRoadCO2() {
        return roadCO2;
    }

    public void setRoadCO2(double roadCO2) {
        this.roadCO2 = roadCO2;
    }

    public double getCO2PerPerson() {
        return CO2PerPerson;
    }

    public void setCO2PerPerson(double cO2PerPerson) {
        this.CO2PerPerson = cO2PerPerson;
    }

    public int getCarsPerPerson() {
        return carsPerPerson;
    }

    public void setCarsPerPerson(int carsPerPerson) {
        this.carsPerPerson = carsPerPerson;
    }
}

Answer 1

我能看到的三个问题。

首先，您永远不会实例化 sc(您将其设置为 null，然后不对其进行任何操作)。

其次，您正在为对象设置 double 值。 (问题更新后不再有效)

第三，您正在将一个对象与一个 double 对象进行比较。

您很可能想比较对象的属性。也许是这样的:

if( arr2[i].getTotalCO2() > highestindex.getTotalCO2() ) {
    highestindex = arr2[i];
}

--编辑--此外，将 highestindex 行更改为:

CO2Data highestindex = arr2[0];