标签：
---Comparable接口-----
public interface Comparable<T> {
int compareTo(T t);
}
---Comparable接口-----
Collections.sort (and Arrays.sort). Objects that implement this interface can be used as keys in a sorted map or as elements in a sorted set, without the need to specify a comparator.public class Employee implements Comparable<Employee> {
private int EmpID ;
private String Ename;
private double Sal ;
private static int i;
public Employee() {
EmpID = i++;
Ename = "dont know";
Sal = 0.0;
}
public Employee(String ename, double sal) {
EmpID = i++;
Ename = ename;
Sal = sal;
}
public String toString() {
return "EmpID " + EmpID + "\n" + "Ename " + Ename + "\n" + "Sal " + Sal ;
}
public int compareTo(Employee arg0) {
// TODO Auto-generated method stub
if (Sal < arg0. Sal)
return -1;
else if (Sal == arg0.Sal)
return 0;
else
return 1;
}
}
然后就可以使用该类了，结合List<T>，Array集合实现对集合中的元素进行排序，如下：
public class ComparableDemo {
public static void main(String[] args) {
List<Employee> ts1 = new ArrayList<Employee>();
ts1.add(new Employee( "Tom", 40000.00));
ts1.add(new Employee( "Harry", 20000.00));
ts1.add(new Employee( "Maggie", 50000.00));
ts1.add(new Employee( "Chris", 70000.00));
Collections.sort(ts1);
Iterator<Employee> itr = ts1.iterator();
System.out.println( "------List--------");
while (itr.hasNext()) {
Object element = itr.next();
System. out.println(element + "\n" );
}
System.out.println( "-----Array--------");
Employee[] oneArray =
{ new Employee("Peter" , 30000.00), new Employee( "Harry", 20000.00),
new Employee("Maggie" , 50000.00)};
Arrays.sort(oneArray);
for (Employee one : oneArray) {
System. out.println(one + "\n" );
}
}
}
Employee one = new Employee( "Tom", 40000.00);
Employee two = new Employee("Chris", 70000.00);
if (one.compareTo( two) == -two .compareTo(one)) {
System. out.println("satisfy rule one." );
}
Employee x = new Employee( "Tom", 40000.00);
Employee y = new Employee( "ChrisY", 30000.00);
Employee z = new Employee( "Chris", 20000.00);
if (x.compareTo(y) > 0 && y.compareTo(z) > 0 && x.compareTo(z) > 0) {
System. out.println("satisfy rule No.two" );
}
Employee x = new Employee( "Tom", 40000.00);
Employee y = new Employee( "ChrisY", 40000.00);
Employee z = new Employee( "Chris", 20000.00);
if (x.compareTo(y) == 0) {
if (x.compareTo(z) == y.compareTo(z)) {
System. out.println("satisfy rule No.threee" );
}
}
public class NewEmployee implements Comparable<NewEmployee> {
public static final int Low = 10;
public static final int Middle = 20;
public static final int High = 30;
private int EmpID ;
private String Ename;
private double Sal ;
private static int i;
private Grade oneGrade;
public NewEmployee() {
EmpID = i++;
Ename = "dont know";
Sal = 0.0;
oneGrade = new Grade( Low );
}
public NewEmployee(String ename, double sal, Grade grade) {
EmpID = i++;
Ename = ename;
Sal = sal;
oneGrade = grade;
}
public String toString() {
return "EmpID " + EmpID + "\n" + "Ename " + Ename + "\n" + "Sal " + Sal + "\n" + "Grade "
+ getGradeName( oneGrade.getGrade());
}
private String getGradeName( int grade) {
switch (grade) {
case Low :
return "Low" ;
case Middle :
return "Middle" ;
case High :
return "High" ;
default:
return "Null" ;
}
}
public int compareTo(NewEmployee arg0) {
// TODO Auto-generated method stub
if ( oneGrade.compareTo(arg0. oneGrade) == 0) {
if ( Sal < arg0. Sal) {
return -1;
} else if (Sal == arg0. Sal) {
return 0;
} else {
return 1;
}
} else {
return oneGrade.compareTo(arg0. oneGrade);
}
}
}
--------
public class NewComparableDemo {
public static void main(String[] args) {
List<NewEmployee> ts1 = new ArrayList<NewEmployee>();
ts1.add( new NewEmployee( "Tom" , 40000.00, new Grade(NewEmployee. Middle)));
ts1.add( new NewEmployee( "Harry" , 20000.00, new Grade(NewEmployee. Low)));
ts1.add( new NewEmployee( "Maggie" , 50000.00, new Grade(NewEmployee. High)));
ts1.add( new NewEmployee( "Chris" , 70000.00, new Grade(NewEmployee. Low)));
Collections. sort(ts1);
Iterator<NewEmployee> itr = ts1.iterator();
while (itr.hasNext()) {
Object element = itr.next();
System. out .println(element + "\n" );
}
NewEmployee x = new NewEmployee( "Tom" , 40000.00, new Grade(NewEmployee.Middle ));
NewEmployee y = new NewEmployee( "Harry" , 20000.00, new Grade(NewEmployee.Low ));
if (x.compareTo(y) == -y.compareTo(x)) {
System. out .println("satisfy rule No.one" );
}
NewEmployee x1 = new NewEmployee( "Tom" , 40000.00, new Grade(NewEmployee.Middle ));
NewEmployee y1 = new NewEmployee( "Harry1" , 70000.00, new Grade(NewEmployee.Low ));
NewEmployee z1 = new NewEmployee( "Harry2" , 30000.00, new Grade(NewEmployee.Low ));
if (x1.compareTo(y1) > 0 && y1.compareTo(z1) > 0 && x1.compareTo(z1) > 0) {
System. out .println("satisfy rule No.two" );
}
NewEmployee x2 = new NewEmployee( "Tom2" , 70000.00, new Grade(NewEmployee.Middle ));
NewEmployee y2 = new NewEmployee( "Harry2" , 70000.00, new Grade(NewEmployee.Middle ));
NewEmployee z2 = new NewEmployee( "Harry2" , 30000.00, new Grade(NewEmployee.Low ));
if (x2.compareTo(y2) == 0) {
if (x2.compareTo(z2) == y2.compareTo(z2)) {
System. out .println("satisfy rule No.three" );
}
}
}
}
标签：
原文地址：http://www.cnblogs.com/ttylinux/p/4375789.html
