java - 返校时间

我正在尝试收集小时。这似乎在此类课程中起作用。现在，我想在另一个类中使用intTime进行一些计算。如何返回intTime。
返回实例的属性时，我尝试使用相同的原理，但是时间与我使用的任何对象都不相关。 getIntTime是否可行？

import java.text.SimpleDateFormat;
import java.util.*;

public class Time extends Database{
    public Time(){
        Calendar cal = Calendar.getInstance();
        SimpleDateFormat sdf = new SimpleDateFormat ("HH:mm:ss");
        String stringTime = sdf.format (cal.getTime());

        int intTime = 0;

        stringTime = stringTime.substring(3,5); // retrieve the minutes (is recorded as string)
        intTime = Integer.parseInt(stringTime);
    }

    public String getStringTime() {
        return intTime;
    }

    public static void main (String[] args) {
    }
}

最佳答案

您需要将intTime定义为类成员。在您的代码中，intTime仅在构造函数内部“存在”。

import java.text.SimpleDateFormat;
import java.util.*;

public class Time extends Database{
    // class member defined in the class but not inside a method.
    private int intTime = 0;
    public Time(){
        Calendar cal = Calendar.getInstance();
        SimpleDateFormat sdf = new SimpleDateFormat ("HH:mm:ss");
        String stringTime = sdf.format (cal.getTime());

        // vars defined here, will be gone when method execution is done.

        stringTime = stringTime.substring(3,5); // retrieve the minutes (is recorded as string)

        // setting the intTime of the instance. it will be available even when method execution is done.
        intTime = Integer.parseInt(stringTime);
    }

    public String getStringTime() {
        return intTime;
    }

    public static void main (String[] args) {
        // code here
    }
}