使用 for 循环和 object 方法将值分配给 Java 中的对象数组时遇到问题

Question

In my Time class i have:

public Time(String start_time) 
    {
    time = start_time;
    hrs = Integer.parseInt(time.substring(0, 2));
    mins = Integer.parseInt(time.substring(3, 5));
    secs = Integer.parseInt(time.substring(6, 8));
    }

and

public void addHour()
  {
    hrs = hrs + 1;

    }
    if (hrs > 23) {
      hrs = hrs - 24;
    }

    prntsecs = String.valueOf(secs);
    prntmins = String.valueOf(mins);
    prnthrs = String.valueOf(hrs);

    if (secs < 10) {
      prntsecs = "0" + String.valueOf(secs);
    }
    if (mins < 10) {
      prntmins = "0" + String.valueOf(mins);
    }
    if (hrs < 10) {
      prnthrs = "0" + String.valueOf(hrs);
    }

    time = prnthrs + ":" + prntmins + ":" + prntsecs;
  }

In my Main class i have:

Time tstamps[] = new Time[5];
Time a = new Time("09:00:00");
for (int i = 0; i < 5; i++){
  tstamps[i] = a;
  a.addHour();
}

tstamps[0].printTime();
tstamps[1].printTime();
tstamps[2].printTime();
tstamps[3].printTime();
tstamps[4].printTime();

I want it to print:

09:00:00
10:00:00
11:00:00
12:00:00
13:00:00

But it prints:

14:00:00
14:00:00
14:00:00
14:00:00
14:00:00

I've tried messing around with the code in my Main class, but I'm very much a beginner, please help me understand my mistake and how to fix it...

Edit:

Sorry, I still don't quite understand how to do this...

I tried to follow your advice and did this:

Time tstamps[] = new Time[5];
    for (int i = 0; i < 5; i++){
      Time a = new Time("09:00:00");
      for (int j = 1; j < i; j++){
        a.addHour();
      }
      tstamps[i] = a;
    }

But now it just prints 09:00:00 five times, instead of 14:00:00.

My field definitions for the Time class:

public String time;
public String prntsecs;
public String prntmins;
public String prnthrs;
public int hrs;
public int mins;
public int secs;

I don't have any for the Main class.

Also, please excuse me if I break any community norms, or something of the sort, this is my second time ever posting on StackOverflow.

Answer 1

Based upon your posted code - but removing the compile error from addHour

and modifying to

    Time tstamps[] = new Time[5];
    for (int i = 0; i < 5; i++){
      Time a = new Time("09:00:00");
      for (int j = 1; j < i + 1; j++){   // changed
        a.addHour();
      }
      tstamps[i] = a;
    }

    for (int x = 0; x < 5; x++) {
        System.out.println(tstamps[x].time);
    }

I get the output

09:00:00
10:00:00
11:00:00
12:00:00
13:00:00

Answer 2

Here's another approach, using your original code.

Time tstamps[] = new Time[5];
Time a = new Time("09:00:00");
for (int i = 0; i < 5; i++){
  tstamps[i] = a;
  a.addHour();
  a = new Time(a.time);
}

Suggestions for improvement(s): Make Time.addHour() return a new Time that is one hour in the future. That would allow you to simplify the above further. Like,

Time tstamps[] = new Time[5];
Time a = new Time("09:00:00");
for (int i = 0; i < 5; i++){
  tstamps[i] = a;
  a = a.addHour();
}

or

Time tstamps[] = new Time[5];
tstamps[0] = new Time("09:00:00");
for (int i = 1; i < tstamps.length; i++) {
  tstamps[i] = tstamps[i-1].addHour();
}