应用场景：
在开发中经常遇到要对List<Object>集合进行排序,并且是根据集合中的对象的某个属性来进行排序 --------以下就此做出的解决方案
public static final String DESC = "desc";
public static final String ASC = "asc"; /**
* 用途:对一个List集合数组进行排序
*
* 说明:
* 目前可以对List<java.lang.Class>、List<POJO>、List<Map>这三种类型集合进行排序
*
* @param list 排序操作的集合对象
* @param property 指定集合中元素的排序字段,如果集合元素不是对象类型可以传值为null
* @param sort 用于指定是升序还是降序 CollectionsUtil.DESC--降序 CollectionsUtil.ASC--升序
* @date 2018.04.27 PM
*/
public static <T> void sortOnList(List<T> list,final Object property,final String sort){
Collections.sort(list,new Comparator<T>(){
@Override
public int compare(T o1, T o2) {
Integer a1 = null;
Integer a2 = null;
if(o1 instanceof Integer) { //针对List<Integer>
a1 = (Integer) o1;
a2 = (Integer) o2;
} else if(o1 instanceof String) { //针对List<String>
a1 = Integer.valueOf(o1.toString());
a2 = Integer.valueOf(o2.toString());
} else if(o1 instanceof Map) { //针对List<Map<String,String>类型
Map temp1 = (Map) o1;
Map temp2 = (Map) o2;
Object object = temp1.get(property);
if(object instanceof Integer) {
a1 = (Integer) object;
a2 = (Integer) temp2.get(property);
} else if(object instanceof String){ //根据Map中value来进行排序String类型需要转换
a1 = Integer.parseInt(object.toString());
a2 = Integer.parseInt(temp2.get(property).toString());
}
} else { //针对对象类型
Class c1 = o1.getClass();
Class c2 = o2.getClass();
try {
Field declaredField1 = c1.getDeclaredField(property.toString());
Field declaredField2 = c2.getDeclaredField(property.toString());
declaredField1.setAccessible(true);
declaredField2.setAccessible(true);
a1 = Integer.parseInt(declaredField1.get(o1).toString());
a2 = Integer.parseInt(declaredField2.get(o2).toString());
} catch (Exception e) {
e.printStackTrace();
}
}
if(sort.equals(CollectionsUtil.ASC)) //升序
return a1.compareTo(a2);
else //降序
return a2.compareTo(a1);
}
});
}
以下代码原理:
Collections.sort(list,new Comparator<T>(){
@Override
public int compare(T o1, T o2){
}
}
根据集合中的元素,把o1与o2对象的某个数值型属性进行对比：
o1 - o2 >= 0 --- 升序
o1 - o2 < 0 --- 降序
sort方法是对List集合中对象某个属性来进行排序的，例如:
package hello1; import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List; import hello.Student; public class Main { public static void main(String[] args) {
Student s1 = new Student();
s1.setId(6); Student s2 = new Student();
s2.setId(66); Student s3 = new Student();
s3.setId(1); Student s4 = new Student();
s4.setId(55); List<Student> list = new ArrayList<>();
list.add(s1);
list.add(s2);
list.add(s3);
list.add(s4); System.out.println("未排序结果:"+ list); //根据Student对象id属性排序
Collections.sort(list, new Comparator<Student>() { @Override
public int compare(Student o1, Student o2) {
return o1.getId() - o2.getId();
} }); System.out.println("排序后结果:"+ list); } }
运行结果 ======================》
欢迎路过的哥们提好建议