我正在尝试按姓氏对数组进行排序，但我在代码中遇到了障碍，我不知道该怎么做，也找不到任何对我有帮助的东西。我的主要问题在于
public void sortByLastName(){
Collections.sort(list);
}
这两段代码在两个不同的类中，有问题吗？
public int compareTo(Person p){
int compareResult = this.lastName.compareTo(p.lastName);
if(compareResult == 0){
return 0;
}
else
if(compareResult > 0){
return 1;
}
else
return -1;
}
}
如果您希望以一种以上的方式对任何内容进行排序，您将很快确定最好的做法是将比较函数作为参数传递给Collections.sort.
public void sortByLastName(){
Collections.sort(list, new Comparator<Person>() {
public int compare(Person lhs, Person rhs){
return lhs.lastName.compareTo(rhs.lastName);
}
} );
}
你可以试试：
public int compareTo(Person p){
return lastName.compareToIgnoreCase(p.lastName);
}
您的compareTo方法需要在您的Person课程中。你的Person班级需要implement Comparable<Person>。Collections.sort然后将工作 -
private static final class Person implements Comparable<Person> {
private String firstName;
private String lastName;
public Person(String firstName, String lastName) {
this.firstName = firstName;
this.lastName = lastName;
}
public String getFirstName() {
return firstName;
}
public void setFirstName(String firstName) {
this.firstName = firstName;
}
public String getLastName() {
return lastName;
}
public void setLastName(String lastName) {
this.lastName = lastName;
}
public int compareTo(Person o) {
int c = getLastName().compareTo(o.getLastName());
if (c != 0) {
return c;
}
return getFirstName().compareTo(o.getFirstName());
}
@Override
public String toString() {
return getFirstName() + " " + getLastName();
}
}
public static void main(String[] args) {
final List<Person> people = new LinkedList<Person>();
people.add(new Person("John", "Smith"));
people.add(new Person("Hans", "Mustermann"));
people.add(new Person("John", "Doe"));
System.out.println(people);
Collections.sort(people);
System.out.println(people);
}
输出：
[John Smith, Hans Mustermann, John Doe]
[John Doe, Hans Mustermann, John Smith]
我已经制作了一个函数，通过模型类中的特定变量对对象列表进行排序。它可能与您需要的不直接匹配，但也许您可以接受这个想法。我正在使用反射来对具有任何数据类型的任何类模型进行排序。
public Vector sort(Vector list, String kelas, String s, String asc) throws NoSuchMethodException {
try {
// Creates an object of type Class which contains the information of
// the class String
Object[] obj = list.toArray();
Object[] args = {};
Class cl = Class.forName(kelas);
Method toSort = cl.getMethod(s, null);
if (asc.equalsIgnoreCase("desc")) {
if (toSort.getReturnType().toString().equalsIgnoreCase("int") || toSort.getReturnType().toString().equalsIgnoreCase("double")) {
for (int i = 0; i < obj.length; i++) {
for (int j = i; j < obj.length; j++) {
try {
if (Double.parseDouble(toSort.invoke(obj[i], args).toString()) < Double.parseDouble(toSort.invoke(obj[j], args).toString())) {
Object temp = obj[i];
obj[i] = obj[j];
obj[j] = temp;
}
} catch (IllegalAccessException ex) {
Logger.getLogger(DbBean.class.getName()).log(Level.SEVERE, null, ex);
} catch (IllegalArgumentException ex) {
Logger.getLogger(DbBean.class.getName()).log(Level.SEVERE, null, ex);
} catch (InvocationTargetException ex) {
Logger.getLogger(DbBean.class.getName()).log(Level.SEVERE, null, ex);
}
}
}
} else {
for (int i = 0; i < obj.length; i++) {
for (int j = i; j < obj.length; j++) {
try {
if (toSort.invoke(obj[i], args).toString().compareToIgnoreCase(toSort.invoke(obj[j], args).toString()) < 0) {
Object temp = obj[i];
obj[i] = obj[j];
obj[j] = temp;
}
} catch (IllegalAccessException ex) {
Logger.getLogger(DbBean.class.getName()).log(Level.SEVERE, null, ex);
} catch (IllegalArgumentException ex) {
Logger.getLogger(DbBean.class.getName()).log(Level.SEVERE, null, ex);
} catch (InvocationTargetException ex) {
Logger.getLogger(DbBean.class.getName()).log(Level.SEVERE, null, ex);
}
}
}
}
} else {
if (toSort.getReturnType().toString().equalsIgnoreCase("int") || toSort.getReturnType().toString().equalsIgnoreCase("double")) {
for (int i = 0; i < obj.length; i++) {
for (int j = i; j < obj.length; j++) {
try {
if (Double.parseDouble(toSort.invoke(obj[i], args).toString()) > Double.parseDouble(toSort.invoke(obj[j], args).toString())) {
Object temp = obj[i];
obj[i] = obj[j];
obj[j] = temp;
}
} catch (IllegalAccessException ex) {
Logger.getLogger(DbBean.class.getName()).log(Level.SEVERE, null, ex);
} catch (IllegalArgumentException ex) {
Logger.getLogger(DbBean.class.getName()).log(Level.SEVERE, null, ex);
} catch (InvocationTargetException ex) {
Logger.getLogger(DbBean.class.getName()).log(Level.SEVERE, null, ex);
}
}
}
} else {
for (int i = 0; i < obj.length; i++) {
for (int j = i; j < obj.length; j++) {
try {
if (toSort.invoke(obj[i], args).toString().compareToIgnoreCase(toSort.invoke(obj[j], args).toString()) > 0) {
Object temp = obj[i];
obj[i] = obj[j];
obj[j] = temp;
}
} catch (IllegalAccessException ex) {
Logger.getLogger(DbBean.class.getName()).log(Level.SEVERE, null, ex);
} catch (IllegalArgumentException ex) {
Logger.getLogger(DbBean.class.getName()).log(Level.SEVERE, null, ex);
} catch (InvocationTargetException ex) {
Logger.getLogger(DbBean.class.getName()).log(Level.SEVERE, null, ex);
}
}
}
}
}
list = new Vector();
for (int i = 0; i < obj.length; i++) {
list.add(obj[i]);
}
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
return list;
}
您可以像这样简单地调用该函数：
Vector sortedList=sort(UnsortedList, "bean.Items", "getItemName", "asc");
此行将根据项目名称升序对我的项目列表（项目是模型类）进行排序