Java Collections sort()
Java Collections 类的
sort()方法用于对指定列表中存在的元素进行排序。有
两种不同类型的Java sort()方法，可以根据其参数进行区分。这些是:
Java Collections sort(list)方法
Java Collections sort(list，comp)方法
Java Collections sort(list)方法
此方法用于按指定的升序对出现在指定集合列表中的元素进行排序。
Java Collections sort(list，comp)方法
此方法用于根据指定比较器引入的顺序对指定列表进行排序。
语法
以下是
sort()方法的声明:
public static <T extends Comparable<? super T>> void sort(List<T> list)
public static <T> void sort(List<T> list, Comparator<? super T> comp)
参数
| 参数 |
说明 |
必需/可选 |
| list |
这是要排序的列表。 |
必需 |
| comp |
由比较器确定列表的顺序。 |
必需 |
返回
sort()方法不返回任何内容。
异常
UnsupportedOperationException -如果指定列表或其列表迭代器不支持set操作，则此方法引发异常。
ClassCastException >-如果列表包含不可相互比较的元素(例如，字符串和整数)，则此方法引发异常。
示例1
import java.util.*;
public class CollectionsSortExample1 {
public static void main(String[] args) {
//Create an array of string objects
String str[] = { "Java","Python","Android","One","Ruby","Node.js"};
//Create list
List<String> list = new ArrayList<>(Arrays.asList(str));
System.out.println("Specified value before sort: "+list);
//Sort the list
Collections.sort(list);
System.out.println("Specified value after sort: "+list);
}
}
输出:
Specified value before sort: [Java, Python, Android, One, Ruby, Node.js]
Specified value after sort: [Android, Java, Node.js, One, Python, Ruby]
示例2
import java.util.*;
public class CollectionsSortExample2 {
public static void main(String[] args) {
//Create an array of string objects
String str[] = { "Java","Python","Android","One","Ruby","Node.js"};
//Create list
List<String> list = new ArrayList<>(Arrays.asList(str));
System.out.println("Value before sort: "+list);
//Sort the list according to specified comparator
Collections.sort(list,Collections.reverseOrder());
System.out.println("Sort Value according to specified comparator: "+list);
}
}
输出:
Value before sort: [Java, Python, Android, One, Ruby, Node.js]
Sort Value according to specified comparator: [Ruby, Python, One, Node.js, Java, Android]
示例3
import java.util.*;
public class CollectionsSortExample3 {
public static void main(String[] args) {
ArrayList<Integer> al=new ArrayList<>();
al.add(Integer.valueOf(201));
al.add(Integer.valueOf(101));
al.add(230);//internally will be converted into objects as Integer.valueOf(230)
Collections.sort(al);
Iterator<Integer> itr=al.iterator();
while(itr.hasNext()){
System.out.println(itr.next());
}
}
}
输出:
示例4
import java.util.*;
public class CollectionsSortExample4 {
public static void main (String[] args)
{
ArrayList<Student> arr = new ArrayList<Student>();
arr.add(new Student(101, "Java", "USA"));
arr.add(new Student(103, "Ruby", "China"));
arr.add(new Student(102, "Android", "India"));
System.out.println("Data before sorted-");
for (int i=0; i<arr.size(); i++)
System.out.println(arr.get(i));
//Sorting data according to specified comparator
Collections.sort(arr, new Sortbyroll());
System.out.println("Data after sorted by rollno-");
for (int i=0; i<arr.size(); i++)
System.out.println(arr.get(i));
}
}
//class which represents a student data.
class Student
{
int rollno;
String name, address;
//Constructor
public Student(int rollno, String name, String address)
{
this.rollno = rollno;
this.name = name;
this.address = address;
}
//Prints student data
public String toString()
{
return this.rollno + " " + this.name + " " + this.address;
}
}
class Sortbyroll implements Comparator<Student>
{
//Used for sorting in ascending order of roll number
public int compare(Student a, Student b)
{
return a.rollno - b.rollno;
}
}
输出:
Data before sorted-
101 Java USA
103 Ruby China
102 Android India
Data after sorted by rollno-
101 Java USA
102 Android India
103 Ruby China
