不兼容的类型，无法转换为 int

Question

Can anyone see why I'm getting the error "Incompatible types, NumberDisplay cannot be converted to int"

The original project did not include seconds so I wanted to add it, but then when I tried, I got the error.

I have tried changing values, did not help.

public class ClockDisplay
{
private NumberDisplay hours;
private NumberDisplay minutes;
private NumberDisplay seconds;
private String displayString;    // simulates the actual display

/**
 * Constructor for ClockDisplay objects. This constructor 
 * creates a new clock set at 00:00.
 */
public ClockDisplay()
{
    hours = new NumberDisplay(24);
    minutes = new NumberDisplay(60);
    seconds = new NumberDisplay(60);
    updateDisplay();
}

/**
 * Constructor for ClockDisplay objects. This constructor
 * creates a new clock set at the time specified by the 
 * parameters.
 */
public ClockDisplay(int hour, int minute, int seconds)
{
    hours = new NumberDisplay(24);
    minutes = new NumberDisplay(60);
    seconds = new NumberDisplay(60);
    setTime(hour, minute);
}

/**
 * This method should get called once every minute - it makes
 * the clock display go one second forward.
 */
public void timeTick()
{
    seconds.increment();
    if(seconds.getValue() == 0) {  // it just rolled over!
        minutes.increment();
    }
    updateDisplay();
}

/**
 * This method should get called once every minute - it makes
 * the clock display go one minute forward.
 */
public void timeTickTwo()
{
    minutes.increment();
    if(minutes.getValue() == 0) {  // it just rolled over!
        hours.increment();
    }
    updateDisplay();
}

/**
 * Set the time of the display to the specified hour and
 * minute.
 */
public void setTime(int hour, int minute, int seconds)
{
    hours.setValue(hour);
    minutes.setValue(minute);
    seconds.setValue(second);
    updateDisplay();
}

/**
 * Return the current time of this display in the format HH:MM.
 */
public String getTime()
{
    return displayString;
}

/**
 * Update the internal string that represents the display.
 */
private void updateDisplay()
{
    displayString = hours.getDisplayValue() + ":" + 
                    minutes.getDisplayValue() + ":" +
                    seconds.getDisplayValue();
}



public class NumberDisplay
{
private int limit;
private int value;

/**
 * Constructor for objects of class NumberDisplay.
 * Set the limit at which the display rolls over.
 */
public NumberDisplay(int rollOverLimit)
{
    limit = rollOverLimit;
    value = 0;
}

/**
 * Return the current value.
 */
public int getValue()
{
    return value;
}

/**
 * Return the display value (that is, the current value as a two-digit
 * String. If the value is less than ten, it will be padded with a leading
 * zero).
 */
public String getDisplayValue()
{
    if(value < 10) {
        return "0" + value;
    }
    else {
        return "" + value;
    }
}

/**
 * Set the value of the display to the new specified value. If the new
 * value is less than zero or over the limit, do nothing.
 */
public void setValue(int replacementValue)
{
    if((replacementValue >= 0) && (replacementValue < limit)) {
        value = replacementValue;
    }
}

/**
 * Increment the display value by one, rolling over to zero if the
 * limit is reached.
 */
public void increment()
{
    value = (value + 1) % limit;
}
}

Answer 1

In this method

public ClockDisplay(int hour, int minute, int seconds)
                                              ^^^^^^^
{
    hours = new NumberDisplay(24);
    minutes = new NumberDisplay(60);
    seconds = new NumberDisplay(60);
    ^^^^^^^
    setTime(hour, minute);
}

The line

    seconds = new NumberDisplay(60);

is attempting to assign a NumberDisplay to seconds , which locally is the argument variable and is an int . You should change this to

    this.hours = new NumberDisplay(24);
    this.minutes = new NumberDisplay(60);
    this.seconds = new NumberDisplay(60);

In general it's OK in a constructor or setter to name the arguments the same as the member variables, but you should get into the habit of always using this. on the left hand of the assignment to avoid exactly this problem.