再举个简单例子然后用程序实现。如公司要将员工进行排序（不要说领导排在前面），假设我们的需求比较复杂。先进行姓排序，谁的姓拼音靠前，谁就排前面。然后对名字进行排序。恩.如果同名，女性排前头。如果名字和性别都相同，年龄小的排前头。ok，一个也不算复杂的需求。
如果对java比较熟悉的会知道java.util.Comparator 接口。要实现里面的函数
int compare(Object o1, Object o2) 返回一个基本类型的整型，返回负数表示o1 小于o2，返回0 表示o1和o2相等，返回正数表示o1大于o2。
于是我们设计的人员类要有几个变量，firstname,lastname,sex,age分别表示姓，名，性别，年龄。
public class Person { String firstname,lastname; Boolean sex; Integer age; public Person(String firstname,String lastname,Boolean sex,Integer age) { this.firstname = firstname; this.lastname = lastname; this.sex = sex; this.age = age; } public String getFirstName() { return firstname; } public String getLastName() { return lastname; } public Boolean getSex() { return sex; } public Integer getAge() { return age; } //为了输入方便，重写了toString() public String toString() { return firstname +" "+lastname+" "+(sex.booleanValue()?"男":"女")+" "+age; } } //end person
下面是要实现比较器
public class Comparators {
public static java.util.Comparator getComparator() {
return new java.util.Comparator() {
public int compare(Object o1, Object o2) {
if (o1 instanceof String) {
return compare( (String) o1, (String) o2);
}else if (o1 instanceof Integer) {
return compare( (Integer) o1, (Integer) o2);
}else if (o1 instanceof Person) {
return compare( (Person) o1, (Person) o2);
}else {
System.err.println("未找到合适的比较器");
return 1;
}
}
public int compare(String o1, String o2) {
String s1 = (String) o1;
String s2 = (String) o2;
int len1 = s1.length();
int len2 = s2.length();
int n = Math.min(len1, len2);
char v1[] = s1.toCharArray();
char v2[] = s2.toCharArray();
int pos = 0;
while (n-- != 0) {
char c1 = v1[pos];
char c2 = v2[pos];
if (c1 != c2) {
return c1 - c2;
}
pos++;
}
return len1 - len2;
}
public int compare(Integer o1, Integer o2) {
int val1 = o1.intValue();
int val2 = o2.intValue();
return (val1 < val2 ? -1 : (val1 == val2 ? 0 : 1));
}
public int compare(Boolean o1, Boolean o2) {
return (o1.equals(o2)? 0 : (o1.booleanValue()==true?1:-1));
}
public int compare(Person o1, Person o2) {
String firstname1 = o1.getFirstName();
String firstname2 = o2.getFirstName();
String lastname1 = o1.getLastName();
String lastname2 = o2.getLastName();
Boolean sex1 = o1.getSex();
Boolean sex2 = o2.getSex();
Integer age1 = o1.getAge();
Integer age2 = o2.getAge();
return (compare(firstname1, firstname2) == 0 ?
(compare(lastname1, lastname2) == 0 ? (compare(sex1, sex2) == 0 ? (compare(age1, age2) == 0 ? 0 :
compare(age1, age2)) :
compare(sex1, sex2)) :
compare(lastname1, lastname2)) :
compare(firstname1, firstname2));
}
};
}
}
compare(Person o1, Person o2)的返回值看起来比较别扭。最简单的是
public int compare(Boolean o1, Boolean o2) { return (o1.equals(o2)? 0 : (o1.booleanValue()==true?1:-1)); }
o1和o2相等返回0，否则o1如果是true 就表示o1大于o2。
public class Main {
public Main() {
}
public static void main(String[] args) {
Person[] person = new Person[] {
new Person("ouyang", "feng", Boolean.TRUE, new Integer(27)),
new Person("zhuang", "gw", Boolean.TRUE, new Integer(27)),
new Person("zhuang", "gw", Boolean.FALSE, new Integer(27)),
new text.Person("zhuang", "gw", Boolean.FALSE, new Integer(2)),
};
for (int i = 0; i < person.length; i++) {
System.out.println("before sort=" + person[i]);
}
java.util.Arrays.sort(person, Comparators.getComparator());
for (int i = 0; i < person.length; i++) {
System.out.println("after sort=" + person[i]);
}
}
}
java代码
before sort=ouyang feng 男 27
before sort=zhuang gw 男 27
before sort=zhuang gw 女 27
before sort=zhuang gw 女 2
after sort=ouyang feng 男 27
after sort=zhuang gw 女 2
after sort=zhuang gw 女 27
after sort=zhuang gw 男 27