1、Comparable介面生命了一個比較兩個物件大小的comparaTo（）方法。

例如：

public class Edge implements Comparable<Edge>{


public  int a;
public  int b;
public int cost;

@Override
public int compareTo(Edge e) {
if(e.cost>this.cost){
return -1;
}else if(e.cost==this.cost){
return 0;
}
else{
return 1;
}
}


}

2、Comparator介面在優先順序列表中用到，作為引數傳遞，裡面的方法是compare（）。後來又在treemap中的建構函式中遇到。

import java.util.Comparator;
import java.util.PriorityQueue;
import java.util.Queue;


public class test {
private String name;
private int population;
public test(String name, int population)
{
this.name = name;
   this.population = population;
}
public String getName()
{
    return this.name;
}


public int getPopulation()
{
    return this.population;
}
public String toString()
{
    return getName() + " - " + getPopulation();
}
public static void main(String args[])
{
Comparator<test> OrderIsdn =  new Comparator<test>(){
public int compare(test o1, test o2) {
// TODO Auto-generated method stub
int numbera = o1.getPopulation();
int numberb = o2.getPopulation();
if(numberb > numbera)
{
return 1;
}
else if(numberb<numbera)
{
return -1;
}
else
{
return 0;
}

}




};
Queue<test> priorityQueue =  new PriorityQueue<test>(11,OrderIsdn);

   

test t1 = new test("t1",1);
test t3 = new test("t3",3);
test t2 = new test("t2",2);
test t4 = new test("t4",0);
priorityQueue.add(t1);
priorityQueue.add(t3);
priorityQueue.add(t2);
priorityQueue.add(t4);
System.out.println(priorityQueue.poll().toString());
}
}