Question

我有一个编程任务，我应该将地震震级的大小与另一个进行比较。我应该使用Comparable接口并实现compareTo方法。地震幅度为float值，compareTo方法应返回int类型。所以我的代码看起来像这样：

 public int compareTo(EarthquakeMarker marker){
    return ((int)this.getMagnitude().compareTo((int)marker.getMagnitude()));     
 }

但我得到一个错误，说我“无法调用int compareTo()到原始类型float”。

这是感兴趣的人的完整代码：

package module6;

import de.fhpotsdam.unfolding.data.PointFeature;
import processing.core.PConstants;
import processing.core.PGraphics;

/** Implements a visual marker for earthquakes on an earthquake map
 * 
 * @author UC San Diego Intermediate Software Development MOOC team
 *
 */
// TODO: Implement the comparable interface
public abstract class EarthquakeMarker extends CommonMarker implements Comparable<EarthquakeMarker>
{

// Did the earthquake occur on land?  This will be set by the subclasses.
protected boolean isOnLand;

// The radius of the Earthquake marker
// You will want to set this in the constructor, either
// using the thresholds below, or a continuous function
// based on magnitude. 
protected float radius;


// constants for distance
protected static final float kmPerMile = 1.6f;

/** Greater than or equal to this threshold is a moderate earthquake */
public static final float THRESHOLD_MODERATE = 5;
/** Greater than or equal to this threshold is a light earthquake */
public static final float THRESHOLD_LIGHT = 4;

/** Greater than or equal to this threshold is an intermediate depth */
public static final float THRESHOLD_INTERMEDIATE = 70;
/** Greater than or equal to this threshold is a deep depth */
public static final float THRESHOLD_DEEP = 300;

// ADD constants for colors


// abstract method implemented in derived classes
public abstract void drawEarthquake(PGraphics pg, float x, float y);


// constructor
public EarthquakeMarker (PointFeature feature) 
{
    super(feature.getLocation());
    // Add a radius property and then set the properties
    java.util.HashMap<String, Object> properties = feature.getProperties();
    float magnitude = Float.parseFloat(properties.get("magnitude").toString());
    properties.put("radius", 2*magnitude );
    setProperties(properties);
    this.radius = 1.75f*getMagnitude();
}

// TODO: Add the method:
 public int compareTo(EarthquakeMarker marker){
    return ((int)this.getMagnitude().compareTo((int)marker.getMagnitude());

 }


// calls abstract method drawEarthquake and then checks age and draws X if needed
@Override
public void drawMarker(PGraphics pg, float x, float y) {
    // save previous styling
    pg.pushStyle();

    // determine color of marker from depth
    colorDetermine(pg);

    // call abstract method implemented in child class to draw marker shape
    drawEarthquake(pg, x, y);

    // IMPLEMENT: add X over marker if within past day      
    String age = getStringProperty("age");
    if ("Past Hour".equals(age) || "Past Day".equals(age)) {

        pg.strokeWeight(2);
        int buffer = 2;
        pg.line(x-(radius+buffer), 
                y-(radius+buffer), 
                x+radius+buffer, 
                y+radius+buffer);
        pg.line(x-(radius+buffer), 
                y+(radius+buffer), 
                x+radius+buffer, 
                y-(radius+buffer));

    }

    // reset to previous styling
    pg.popStyle();

}

/** Show the title of the earthquake if this marker is selected */
public void showTitle(PGraphics pg, float x, float y)
{
    String title = getTitle();
    pg.pushStyle();

    pg.rectMode(PConstants.CORNER);

    pg.stroke(110);
    pg.fill(255,255,255);
    pg.rect(x, y + 15, pg.textWidth(title) +6, 18, 5);

    pg.textAlign(PConstants.LEFT, PConstants.TOP);
    pg.fill(0);
    pg.text(title, x + 3 , y +18);


    pg.popStyle();

}


/**
 * Return the "threat circle" radius, or distance up to 
 * which this earthquake can affect things, for this earthquake.   
 * DISCLAIMER: this formula is for illustration purposes
 *  only and is not intended to be used for safety-critical 
 *  or predictive applications.
 */
public double threatCircle() {  
    double miles = 20.0f * Math.pow(1.8, 2*getMagnitude()-5);
    double km = (miles * kmPerMile);
    return km;
}

// determine color of marker from depth
// We use: Deep = red, intermediate = blue, shallow = yellow
private void colorDetermine(PGraphics pg) {
    float depth = getDepth();

    if (depth < THRESHOLD_INTERMEDIATE) {
        pg.fill(255, 255, 0);
    }
    else if (depth < THRESHOLD_DEEP) {
        pg.fill(0, 0, 255);
    }
    else {
        pg.fill(255, 0, 0);
    }
}


/** toString
 * Returns an earthquake marker's string representation
 * @return the string representation of an earthquake marker.
 */
public String toString()
{
    return getTitle();
}
/*
 * getters for earthquake properties
 */

public float getMagnitude() {
    return Float.parseFloat(getProperty("magnitude").toString());
}

public float getDepth() {
    return Float.parseFloat(getProperty("depth").toString());   
}

public String getTitle() {
    return (String) getProperty("title");   

}

public float getRadius() {
    return Float.parseFloat(getProperty("radius").toString());
}

public boolean isOnLand()
{
    return isOnLand;
}

}

Answer 1

有一个内置的静态便利函数Float.compare(float, float)，用于比较基本浮点数：

public int compareTo(EarthquakeMarker marker){
    return Float.compare(this.getMagnitude(), marker.getMagnitude());
}

Answer 2

如消息所示，您无法调用基本类型的方法。

您应该自己实施compareTo()因为它很简单，我认为每次Integer调用compareTo()这样的对象都会花费太多。

public int compareTo(EarthquakeMarker marker){
    int t = (int)this.getMagnitude()
    int m = (int)marker.getMagnitude();
    if (t > m) return 1;
    if (t < m) return -1;
    return 0;
}

尝试将float转换为int时遇到问题

2 个答案: