【发布时间】：2012-09-26 01:45:33
【问题描述】：
我创建了一组 Song 对象。一首歌包含变量标题、作者、解释器、(int)yearReleased、专辑和文件名。我正在使用 main 方法来测试我的歌曲数组和 equals 方法。该测试应该用五个歌曲对象填充一个数组，并使用我的 equals 方法来确保新条目不是先前条目的重复。我的测试类可以编译，但是当我输入重复的歌曲信息时，我不断收到错误消息。如果有人能给我提示或指出正确的方向，我将不胜感激。任何其他提示也会很棒。作为一名学生，很高兴听到专业人士在现实世界中提出的良好建议。
import java.util.Scanner;
public class Test{
public static void main(String[] args)
{
Scanner kybd = new Scanner(System.in);
Song[] songTest = new Song[5];
boolean match;
int count = 0;
System.out.println("Enter 5 songs\n");
for(Song x:songTest)
{
do{
match = false;
x = new Song();
System.out.print("Title: ");
x.setTitle(kybd.nextLine());
System.out.print("Author: ");
x.setAuthor(kybd.nextLine());
System.out.print("Interpreter: ");
x.setInterpreter(kybd.nextLine());
System.out.print("Year released: ");
x.setYearReleased(kybd.nextInt());
kybd.nextLine();
System.out.print("Album: ");
x.setAlbum(kybd.nextLine());
System.out.print("File name: ");
x.setFileName(kybd.nextLine());
System.out.print(x);
System.out.println();
for(int i = 0; i<count; i++)
if(songTest[i].equals(x)){
match = true;
System.out.print("Duplicate");
}
}while(match);
count++;
}
}
}
public class Song
{
public String title;
public String author;
public String interpreter;
public int yearReleased;
public String album;
public String fileName;
//private vars
private int reviewScore = 0;
private int reviews = 0;
private double average;
//Mutator methods
public void setTitle(String t)
{
this.title = t;
}
public void setAuthor(String a)
{
this.author = a;
}
public void setInterpreter(String i)
{
this.interpreter = i;
}
public void setYearReleased(int y)
{
if (y>0)
this.yearReleased = y;
else
{
System.out.print ("This song is not that old");
this.yearReleased = -5;
}
}
public void setAlbum(String a)
{
this.album = a;
}
public void setFileName(String f)
{
this.fileName = f;
}
public void addReviewScore(int s)
{
if (s>0 && s<6)
{
this.reviewScore += s;
this.reviews++;
}
else
System.out.print("This is not a valid review score!");
}
//Accessor methods
public String getTitle()
{
return this.title;
}
public String getAuthor()
{
return this.author;
}
public String getInterpreter()
{
return this.interpreter;
}
public int getYearReleased()
{
return this.yearReleased;
}
public String getAlbum()
{
return this.album;
}
public String getFileName()
{
return this.fileName;
}
public double getAverage()
{
this.average = this.calculateAverage();
return this.average;
}
//Methods
public boolean equals(Song otherSong)
{
boolean isEqual = false;
//compare this song to the otherSong
isEqual =
this.title == otherSong.title &&
this.author == otherSong.author &&
this.interpreter == otherSong.interpreter &&
this.yearReleased == otherSong.yearReleased &&
this.album == otherSong.album &&
this.fileName == otherSong.fileName;
return isEqual;
}
public String toString()
{
String songInfo;
songInfo =
"***Song information***\n" +
"Title: " + this.title +
"\nAuthor: " + this.author +
"\nInterpreter: " + this.interpreter +
"\nYear Released: " + this.yearReleased +
"\nAlbum: " + this.album +
"\nFile name: " + this.fileName +
"\nYears old: " + this.yearsOld();
return songInfo;
}
public int yearsOld()
{
int yearsOld = (2012 - this.yearReleased);
return yearsOld;
}
//Private methods
private double calculateAverage()
{
this.average = ((double)this.reviewScore/(double)this.reviews);
return this.average;
}
}
【问题讨论】：
-
“我不断收到错误”。当某些事情没有按照您的预期工作时，请始终完整描述您的预期和实际结果，和/或在“发生错误”时提供堆栈跟踪。
-
对于
String比较，您应该始终使用equals()方法来比较两个字符串的值，而不是==。==比较两个字符串对象是否指向相同的内存位置。equals()进行实际值比较。 -
您确定您知道比较字符串的正确方法是什么吗？你的 equals 方法对我来说似乎有问题。在 Google 或 StackOverflow 中简单搜索一下“Java 字符串比较”
-
仅供参考，如果您使用 netbeans IDE，它会自动为您生成 equals 方法的原型。但这个练习的重点是学习如何去做。
-
如果您覆盖 equals()，请确保您遵循 hashcode contract。