标签:numbers double less com tom student objects color imp
这个课程的参考视频和图片来自youtube。
主要学到的知识点有:
Build in functions in java.util.Collections
1. Sorting: arrange a collection in order Collections.sort(List<T> list, Comparator<>)
It is used like below:
ArrayList<integer> numbers = new ArrayList<>(); for (int i =0; i< 20; i++){ numbers.add(generator.nextInt(100) + 1); // get a random number from 1 to 100 } Collections.sort(numbers, new IntegerComparator())
Then we create a comparator, defined in another java class called IntegerComparator
public class IntegerComparator implements Comparator<integer>{
@Override public int compare(Integer a, Integer b){ return a-b; } }
If sometimes we need to compare two objects of a customed class.
import java.util.Comparator; public class StudentGpaComparator implements Comparator<Student>{ @Override public int compare(Student s1, Student s2){ double gpa1 = s1.getGpa(); double gpa2 = s2.getGpa(); return (int) ((gpa1 - gpa2)*100) } }
2. Search: find a specific value in a collections Collections.binarySearch(List<T> list, T key, Comparator<>)
It is used like below: (will return -1 if not found)
Collections.binarySearch(numbers, 50, new IntegerComparator());
[Java in NetBeans] Lesson 15. Sorting and Searching.
标签:numbers double less com tom student objects color imp
原文地址:https://www.cnblogs.com/Johnsonxiong/p/10147294.html