Arrays.sort(T[], Comparator < ? super T > c) 方法用于對象數組按用戶自定義規則排序。
Collections.sort(List<T>, Comparator < ? super T > c)方法用于對象集合按用戶自定義規則排序。
Comparable用在對象本身，說明這個對象是可以被比較的，也就是說可以被排序的。（String和Integer之所以可以比較大小，是因為它們都實現了Comparable接口，并實現了compareTo()方法）。
Compator用在對象外，相當于定義了一個排序算法。
還是代碼來的直接：
package com.zx.ww.comparable;
import java.util.Arrays;
import java.util.Comparator;
public class ComparatorTest {
public static void main(String[] args) {
Dog d1 = new Dog(2);
Dog d2 = new Dog(1);
Dog d3 = new Dog(3);
Dog[] dogArray = {d1, d2, d3};
printDogs(dogArray);
Arrays.sort(dogArray, new DogSizeComparator());
printDogs(dogArray);
}
public static void printDogs(Dog[] dogArray) {
for (Dog dog : dogArray) {
System.out.print(dog.size+" ");
}
System.out.println();
}
}
class Dog{
int size;
public Dog(int size) {
this.size = size;
}
}
class DogSizeComparator implements Comparator<Dog> {
@Override
public int compare(Dog dog1, Dog dog2) {
// TODO Auto-generated method stub
return dog1.size - dog2.size;
}
}
輸出結果：
2 1 3
1 2 3
這是對象數組用了Comparator的結果。
下面看對象自身實現了Comparable接口的方式：
/**
*
*/
package com.zx.ww.comparable;
import java.util.Arrays;
/**
* @author wuwei
* 2014年9月29日
*/
public class User implements Comparable<Object>{
private int id;
private String name;
private int age;
public User(int id, String name, int age) {
this.id = id;
this.name = name;
this.age = age;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
@Override
public int compareTo(Object o) {
// TODO Auto-generated method stub
return this.age - ((User)o).getAge();
}
public static void main(String[] args) {
User[] users = new User[] {new User(1,"zhangsan",28), new User(2,"lisi",25)};
Arrays.sort(users);
for (int i = 0; i < users.length; i++) {
User user = users[i];
System.out.println(user.getId()+" "+user.getAge());
}
}
}
輸出結果：
2 25
1 28
上述都是Arrays.sort()的應用方式，同理Collections.sort()一樣的實現，代碼如下，比較簡單：
package com.zx.ww.comparable;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
public class CollectionSortTest {
public static void main(String[] args) {
List<String> list = new ArrayList<String>();
list.add("ac");
list.add("ab");
list.add("aa");
list.add("db");
list.add("ca");
for (String string : list) {
System.out.print(string + " ");
}
System.out.println();
Collections.sort(list);
for (String string : list) {
System.out.print(string + " ");
}
System.out.println();
//對象A自身實現Comparable接口
List<A> aList = new ArrayList<A>();
aList.add(new A("wuwei", 1));
aList.add(new A("zhangsan", 3));
aList.add(new A("lisi", 2));
for (A a : aList) {
System.out.print(a+" ");
}
System.out.println();
Collections.sort(aList);
for (A a : aList) {
System.out.print(a+" ");
}
System.out.println();
//重寫Conparator接口方法
List<B> bList = new ArrayList<B>();
bList.add(new B("wuwei", 1));
bList.add(new B("zhangsan", 3));
bList.add(new B("lisi", 2));
for (B b : bList) {
System.out.print(b+" ");
}
System.out.println();
Collections.sort(bList, new Comparator<B>() {
@Override
public int compare(B b1, B b2) {
// TODO Auto-generated method stub
return b1.getCount().compareTo(b2.getCount());
}
});
for (B b : bList) {
System.out.print(b+" ");
}
System.out.println();
}
}
//對象A自身實現Comparable接口
class A implements Comparable<A>{
private String name;
private Integer order;
public A(String name, Integer order) {
this.name = name;
this.order = order;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Integer getOrder() {
return order;
}
public void setOrder(Integer order) {
this.order = order;
}
public String toString() {
return "name is " +name+" order is "+order;
}
@Override
public int compareTo(A o) {
// TODO Auto-generated method stub
return this.order.compareTo(o.getOrder());
}
}
class B{
private String name;
private Integer count;
public B(String name, Integer count) {
this.name = name;
this.count = count;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Integer getCount() {
return count;
}
public void setCount(Integer count) {
this.count = count;
}
public String toString() {
return "name is "+name+" count is "+count;
}
}
輸出結果：
ac ab aa db ca
aa ab ac ca db
name is wuwei order is 1 name is zhangsan order is 3 name is lisi order is 2
name is wuwei order is 1 name is lisi order is 2 name is zhangsan order is 3
name is wuwei count is 1 name is zhangsan count is 3 name is lisi count is 2
name is wuwei count is 1 name is lisi count is 2 name is zhangsan count is 3
posted on 2014-09-29 16:08
小人物_Amor 閱讀(1118)
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