java - 从对象内部输出数据(JAVA)

Question

我正在尝试将对象内的一些数据输出到控制台。似乎有效，但在数据下方我收到一条奇怪的消息。

下面是代码:

import java.text.DecimalFormat;

/**
 * The Circle class calculates area, diameter, and circumference 
 */

public class Circle {

    DecimalFormat fmt = new DecimalFormat("#0.00");

    // Fields
    private double radius;                  // Holds the circle radius
    private final double PI = 3.14159;      // The formula for PI


    /**
     *      Start Constructors
     */


    public Circle(double rad) {

        radius = rad;
        System.out.println("The circle's radius is " + (fmt.format(radius)));
        System.out.println("The circle's area is " + (fmt.format(PI * radius * radius)));
        System.out.println("The circle's diameter is " + (fmt.format(radius * 2)));
        System.out.println("The circle's circumference is " + (fmt.format(2 * PI * radius)));
    }


}

控制台输出为:

The circle's radius is 2.00
The circle's area is 12.57
The circle's diameter is 4.00
The circle's circumference is 12.57
Circle@5115a298

什么是圈子消息？

Answer 1

为您的 Circle 类提供一个合适的 toString() 方法重写。您将看到此方法的 Object 默认版本的返回结果。

@Override
public String toString() {
   /*  return a String that shows the "state" of this object */
}