o1==>zhang2 22 96.0 o2==>zhang1 20 90.0 o1==>zhang3 23 92.0 o2==>zhang2 22 96.0 o1==>zhang3 23 92.0 o2==>zhang2 22 96.0 o1==>zhang3 23 92.0 o2==>zhang1 20 90.0 o1==>zhang4 22 100.0 o2==>zhang3 23 92.0 o1==>zhang4 22 100.0 o2==>zhang2 22 96.0 ======================================================== zhang1 20 90.0 zhang3 23 92.0 zhang2 22 96.0 zhang4 22 100.0
今天项目用到比较器,在网上搜了好些都没有详细的说明,所以我在仿照提供的demo做了下:
package www.zz.com; import java.util.Comparator; public class StudentTest { private String name; private int age; private float score; public StudentTest(String name, int age, float score) { this.name = name; this.age = age; this.score = score; } 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; } public float getScore() { return score; } public void setScore(float score) { this.score = score; } public String toString() { return name+"\t\t"+age+"\t\t"+score; } public static void main(String[] args) { StudentTest stu[] = { new StudentTest("zhang1", 20, 90.0f), <span style="white-space:pre"> </span>new StudentTest("zhang2", 22, 91.0f), <span style="white-space:pre"> </span>new StudentTest("zhang3", 23, 99.0f), <span style="white-space:pre"> </span>new StudentTest("zhang4", 22, 100.0f) }; java.util.Arrays.sort(stu, new StudentComparator()); System.out.println(); System.out.println(); System.out.println(); System.out.println(); System.out.println(); System.out.println("========================================================"); for (StudentTest s : stu) { System.out.println(s); } } } class StudentComparator implements Comparator{ public int compare(Object obj1, Object obj2) { StudentTest o1= (StudentTest) obj1; StudentTest o2= (StudentTest) obj2; System.out.println("o1==>"+o1.toString()); System.out.println("o2==>"+o2.toString()); if(o1.getScore()>o2.getScore()) return 1; else if(o1.getScore()<o2.getScore()) return -1; else{ if(o1.getAge()>o2.getAge()) return 1; else if(o1.getAge()<o2.getAge()) return -1; else return 0; } } }
</pre><pre name="code" class="java">
结果:
o1==>zhang2 22 96.0
o2==>zhang1 20 90.0
o1==>zhang3 23 92.0
o2==>zhang2 22 96.0
o1==>zhang3 23 92.0
o2==>zhang2 22 96.0
o1==>zhang3 23 92.0
o2==>zhang1 20 90.0
o1==>zhang4 22 100.0
o2==>zhang3 23 92.0
o1==>zhang4 22 100.0
o2==>zhang2 22 96.0
=======================================================
zhang1 20 90.0
zhang3 23 92.0
zhang2 22 96.0
zhang4 22 100.0
由上面样例我总结了一下:
就是在compare方法内,每次比较是先去后面的值赋给o1,在取前面的值赋给o2,
可以认为目前顺序是o2在前,o1在后,
o1的比较属性比o2大即(o1.getScore()>o2.getScore()),如果结果为true,说明 o1.getScore()-o2.getScore()>0,本身就是符合小的在前面大的在后面的降序排列,即排序后应该还是o2在前,在此时返回1,则应该是升序排列,若是想倒序排列(大的在前,小的灾后即o1在前,o2在后的顺序),则此时返回-1即可(就是告诉程序我不服你的这种安排,我就要给他改变)