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）