上次总结了一下集合的相关内容,这次总结一下,集合的操作类Collection类。
Collections简介如下:
Collections的一些常用操作:
具体代码中的应用如下:
public class Test8 { public static void main(String[] args) { List<String> list = new ArrayList<String>(); list.add("ada"); list.add("bb"); list.add("cc"); list.add("dd"); list.add("ee"); System.out.println(list); Collections.reverse(list);//反转list集合 System.out.println(list); Collections.shuffle(list);//对list集合进行随机排序 System.out.println(list); Collections.sort(list);//对List集合进行字典升序排列 System.out.println(list); Collections.swap(list, 0, 1);//交换指定位置元素 System.out.println(list); System.out.println(Collections.max(list));//返回最大值 System.out.println(Collections.frequency(list,"ada"));//返回指定元素出现次数 Collections.replaceAll(list, "cc", "bb");//替换元素 Student s1 = new Student("张三",13); Student s2 = new Student("赵四",19); Student s3 = new Student("王五",17); Student s4 = new Student("孙六",16); Student s5 = new Student("吴七",23); List<Student> stu = new ArrayList<Student>(); stu.add(s1); stu.add(s2); stu.add(s3); stu.add(s4); stu.add(s5); for(Student st:stu) { System.out.println(st.name+" "+st.age); } System.out.println("=============================="); Collections.sort(stu,new Student());//通过年龄从小到大排序 for(Student st:stu) { System.out.println(st.name+" "+st.age); } Student s = Collections.max(stu, new Student()); System.out.println(s.name+" "+s.age); } } class Student implements Comparator<Student>{//通过年龄从小到大排序 int age; String name; public Student() { } public Student(String name,int age) { this.age = age; this.name = name; } @Override public int compare(Student arg0, Student arg1) { if(arg0.age > arg1.age) { return 1; }else if(arg0.age < arg1.age) { return -1; } else { return 0; } } }