学步园

/**
* Created by IntelliJ IDEA.
* User: leizhimin
* Date: 2008-3-29 22:21:19
* Company: LavaSoft([url]http://lavasoft.blog.51cto.com[/url])
* 要排序的元素对象
*/
public class Cat
implements Comparable<Cat> {
    private int age;

    private String name;

    public Cat(int age, String name) {

        this.age = age;
        this.name = name;
    }

    public int getAge() {

        return age;
    }

    public void setAge(int age) {

        this.age = age;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {

        this.name = name;
    }

    public String toString() {
        return "Cat{" +

                "age=" + age +
                ", name='" + name + '\'' +
                '}';
    }

    public int compareTo(Cat o) {

        return this.getAge() - o.getAge();

    }
}

调用Collections.sort(List<T> list)排序：
Cat{age=12, name='haha'}
Cat{age=23, name='leizhimin'}
Cat{age=34, name='hehe'}

逆序排列元素:
Cat{age=34, name='hehe'}
Cat{age=23, name='leizhimin'}
Cat{age=12, name='haha'}

再次逆序排列元素:
Cat{age=12, name='haha'}
Cat{age=23, name='leizhimin'}
Cat{age=34, name='hehe'}

添加一个元素后输出集合：
Cat{age=12, name='haha'}
Cat{age=23, name='leizhimin'}
Cat{age=34, name='hehe'}
Cat{age=13, name='lavasoft'}

排列后输出:
Cat{age=12, name='haha'}
Cat{age=13, name='lavasoft'}
Cat{age=23, name='leizhimin'}
Cat{age=34, name='hehe'}

-------------数组转换为列表-------------
z
a
C

-------------列表转换为数组(1)-------------
z
a
C
-------------列表转换为数组(2)-------------
z
a
C
-------------顺序排序列表-------------
C
a
z

-----按String实现的Comparator对象String.CASE_INSENSITIVE_ORDER排序----
a
C
z

-------------倒序排序列表-------------
z
a
C

-----按String实现的Comparator对象String.CASE_INSENSITIVE_ORDER排序----
a
C
z

-----反转列表元素的顺序------
z
C
a

Process finished with exit code 0

/**
* Created by IntelliJ IDEA.
* User: leizhimin
* Date: 2008-3-29 13:28:29
* Company: LavaSoft([url]http://lavasoft.blog.51cto.com[/url])
* 要排序的元素对象
*/
public class Person {

    private int age;

    private String name;

    public Person(int age, String name) {

        this.age = age;
        this.name = name;
    }

    public int getAge() {

        return age;
    }

    public void setAge(int age) {

        this.age = age;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {

        this.name = name;
    }

    public String toString() {
        return "Person{" +

                "age=" + age +
                ", name='" + name + '\'' +
                '}';
    }
}

import java.util.Comparator;

/**
* Created by IntelliJ IDEA.
* User: leizhimin
* Date: 2008-3-29 13:29:35
* Company: LavaSoft([url]http://lavasoft.blog.51cto.com[/url])
* Person类的排序接口
*/
public class PersonComparator
implements Comparator<Person> {
    /**
     * 排序接口算法实现
     *
     * @param o1
     * @param o2
     * @return 比较结果的大小
     */
    public int compare(Person o1, Person o2) {

        return o1.getAge() - o2.getAge();
    }
}

import collsort.compare.Person;

import java.util.*;

/**
* Created by IntelliJ IDEA.
* User: leizhimin
* Date: 2008-3-29 13:30:49
* Company: LavaSoft([url]http://lavasoft.blog.51cto.com[/url])
* 通过Comparator接口实现个性化排序测试
* 结论:Comparator接口是一个为集合对象排序的基本算法,其中的compare方法是比较两个元素对象的比较方式.Java Collection框架利用这个算法实现了不同集合类型对象排序方式的统一.<br>

* 排序针对的是确切的集合对象,当集合对象的元素发生变化时,集合内的元素不会自动重新排序.
*/
public class TestComparator {

    public static String outCollection(Collection coll) {

        StringBuffer sb = new StringBuffer();
        for (Object obj : coll) {
            sb.append(obj + "\n");
        }
        System.out.println(sb.toString());
        return sb.toString();
    }

    public static
void main(String args[]) {
        test1();
    }

    public static
void test1() {
        System.out.println("----------test1()---------");

        System.out.println("升序排序测试:");
        List<Person> listPerson = new ArrayList<Person>();

        Person person1 = new Person(34,
"lavasoft");
        Person person2 = new Person(12,
"lavasoft");
//        Person personx = new Person(12, "lavasoft");

        Person person3 = new Person(23,
"leizhimin");
        Person person4 = new Person(13,
"sdg");

        listPerson.add(person1);
        listPerson.add(person2);
        listPerson.add(person3);
//        listPerson.add(personx);

        Comparator<Person> ascComparator = new PersonComparator();

        System.out.println("原集合为:");
        outCollection(listPerson);

        System.out.println("排序后集合为:");
        //利用Collections类静态工具方法对集合List进行排序
        Collections.sort(listPerson, ascComparator);
        outCollection(listPerson);

        System.out.println("在继续添加一个Person对象,集合为:");

        listPerson.add(person4);
        outCollection(listPerson);

        System.out.println("添加一个对象后,重新排序输出:");

        Collections.sort(listPerson, ascComparator);
        outCollection(listPerson);

        System.out.println("\n降序排序测试:");
        //从升序排序对象产生一个反转(降序)的排序对象
        Comparator<Person> descComparator = Collections.reverseOrder(ascComparator);

        System.out.println("利用反转后的排序接口对象对集合List排序并输出:");

        Collections.sort(listPerson, descComparator);
        outCollection(listPerson);

        System.out.println("\n求最大最小元素测试:");
        Person p_max = Collections.max(listPerson, ascComparator);
        Person p_min = Collections.min(listPerson, ascComparator);
        System.out.println("最大元素为:" + p_max.toString());

        System.out.println("最小元素为:" + p_min.toString());

    }
}

排序后集合为:
Person{age=12, name='lavasoft'}
Person{age=23, name='leizhimin'}
Person{age=34, name='lavasoft'}

在继续添加一个Person对象,集合为:
Person{age=12, name='lavasoft'}
Person{age=23, name='leizhimin'}
Person{age=34, name='lavasoft'}
Person{age=13, name='sdg'}

添加一个对象后,重新排序输出:
Person{age=12, name='lavasoft'}
Person{age=13, name='sdg'}
Person{age=23, name='leizhimin'}
Person{age=34, name='lavasoft'}

降序排序测试:
利用反转后的排序接口对象对集合List排序并输出:
Person{age=34, name='lavasoft'}
Person{age=23, name='leizhimin'}
Person{age=13, name='sdg'}
Person{age=12, name='lavasoft'}

求最大最小元素测试:
最大元素为:Person{age=34, name='lavasoft'}
最小元素为:Person{age=12, name='lavasoft'}

Process finished with exit code 0