以下代码编译，但sortTitles（）方法不按照预期的字母顺序对电影的标题进行排序。你会如何修复compareTo（）和sortTitles（）方法？
Movie2 Class
public class Movie2 implements Comparable<Movie2> {
// instance variables
private String title;
private int year;
private String studio;
public Movie2(String title, int year, String studio) {
// initialise instance variables
this.title = title;
this.year = year;
this.studio = studio;
}
public String toString() {
String listing;
listing = title + ", " + year + ", " + studio;
return listing;
}
public void setTitle(String title) {
this.title = title;
}
public String getTitle() {
return title;
}
public void setYear(int year) {
this.year = year;
}
public int getYear() {
return year;
}
public void setStudio(String studio) {
this.studio = studio;
}
public String getStudio() {
return studio;
}
public int compareTo(Movie2 obj) {
if (title < obj.getTitle()) {
return -1;
}
else {
return 1;
}
}
}
TestMovie2类
public class TestMovie2 {
public static void main(String[] args) {
Movie2[] myMovies = new Movie2[10];
Movie2[] sorted = new Movie2[10];
myMovies[0] = new Movie2("The Muppets Take Manhattan", 2001, "Columbia Tristar");
myMovies[1] = new Movie2("Mulan Special Edition", 2004, "Disney");
myMovies[2] = new Movie2("Shrek 2", 2004, "Dreamworks");
myMovies[3] = new Movie2("The Incredibles", 2004, "Pixar");
myMovies[4] = new Movie2("Nanny McPhee", 2006, "Universal");
myMovies[5] = new Movie2("The Curse of the Were-Rabbit", 2006, "Aardman");
myMovies[6] = new Movie2("Ice Age", 2002, "20th Century Fox");
myMovies[7] = new Movie2("Lilo & Stitch", 2002, "Disney");
myMovies[8] = new Movie2("Robots", 2005, "20th Century Fox");
myMovies[9] = new Movie2("Monsters Inc.", 2001, "Pixar");
System.out.println(" Movies ");
System.out.println("______________________________");
System.out.println();
printMovies(myMovies);
System.out.println();
System.out.println();
Movie2[] dest = new Movie2[myMovies.length];
sortTitles(myMovies, dest);
System.out.println(" Sorted by title - ascending ");
System.out.println("______________________________");
System.out.println();
printMovies(myMovies);
System.out.println();
System.out.println();
sortYears(myMovies, sorted);
System.out.println(" Sorted by year - descending");
System.out.println("______________________________");
System.out.println();
printMovies(sorted);
System.out.println();
System.out.println();
}
public static void sortTitles(Movie2[] myMovies, Movie2[] dest) {
for (int i = 0; i < myMovies.length; i++) {
Movie2 next = myMovies[i];
int insertIndex = 0;
int k = i;
while (k > 0 && insertIndex == 0) {
if (myMovies[k].getTitle().compareTo(dest[k - 1].getTitle()) < 1) {
insertIndex = k;
}
else {
dest[k] = dest[k - 1];
}
k--;
}
dest[insertIndex] = next;
}
}
public static void printMovies(Movie2[] sorted) {
for (int i = 0; i < sorted.length; i++)
System.out.println(sorted[i]);
}
public static void sortYears(Movie2[] myMovies, Movie2[] sorted) {
for (int i = 0; i < myMovies.length; i++) {
Movie2 next = myMovies[i];
int insertindex = 0;
int k = i;
while (k > 0 && insertindex == 0) {
if (next.getYear() < sorted[k - 1].getYear()) {
insertindex = k;
}
else {
sorted[k] = sorted[k - 1];
}
k--;
}
sorted[insertindex] = next;
}
}
}
答案 0 :(得分：1)
使用已定义的String的compareTo方法，如：
public int compareTo(Movie2 obj) {
return this.getTitle().compareTo(obj.getTitle());
}
在sortTitles方法中，使用
Arrays.sort(myMovies);//you dont need seperate dest array
答案 1 :(得分：1)
public int compareTo(Movie2 obj)
{
if (title != null)
return title.compareTo(obj.getTitle());
else
return obj.getTitle() == null ? 0 : -1;
}
Java不支持运算符重载。因此，您无法将String与关系运算符进行比较。你应该在那里得到编译时错误。
答案 2 :(得分：0)
首先在compareTo中修复您的Movie2方法（您可能已经完成了，或者它甚至无法编译）：
public int compareTo(Movie2 obj)
{
return title.compareTo(obj.getTitle());
}
然后sortTitles中的TestMovie2方法：
public static void sortTitles(Movie2[] myMovies, Movie2[] dest)
{
for (int i = 0; i < myMovies.length; i++)
{
Movie2 next = myMovies[i];
int insertIndex = 0;
int k = i;
while (k>0 && insertIndex == 0)
{
if (next.getTitle().compareTo(dest[k-1].getTitle()) > -1)
{
System.out.println("less than or equal");
insertIndex = k;
}
else
{
System.out.println("greater than");
dest[k] = dest[k-1];
}
k--;
}
dest[insertIndex] = next;
}
}
你应该得到：
Sorted by title - ascending
______________________________
Ice Age, 2002, 20th Century Fox
Lilo & Stitch, 2002, Disney
Monsters Inc., 2001, Pixar
Mulan Special Edition, 2004, Disney
Nanny McPhee, 2006, Universal
Robots, 2005, 20th Century Fox
Shrek 2, 2004, Dreamworks
The Curse of the Were-Rabbit, 2006, Aardman
The Incredibles, 2004, Pixar
The Muppets Take Manhattan, 2001, Columbia Tristar
答案 3 :(得分：0)
为什么要将String对象与关系运算符进行比较？您也可以将方法命名为与现有方法相同的方法。那么在你的情况下发生的是你的代码没有从TestingMovie2类调用方法。它调用默认的java.lang.String方法。更改名称并使用String类的 comapreTo 方法。将方法修改为：
public int movieCompareTo(Movie2 obj)
{
if (title.comapreTo(obj.getTitle()) < 0)
return -1;
else
return 1;
}
comapreTo 方法:(来自JavaDoc）