注：调用此方法时需要根据自己的须由复写Objects的equals方法

创建复写了equals方法的对象类

public class Student {    private String name;    private int age;    public Student() {    }    public Student(String name, int age) {        this.name = name;        this.age = age;    }    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }    public Integer getAge() {        return age;    }    public void setAge(Integer age) {        this.age = age;    }    @Override    public boolean equals(Object obj) {        Student s = (Student) obj;        return this.name == s.name && this.age == s.age;    }}

调用

import java.util.ArrayList;import java.util.Collections;import java.util.List;public class StudentTest {    public static void main(String[] args) {        List
     
       list = new ArrayList
      
       ();        list.add(new Student("林青霞", 27));        list.add(new Student("风清扬", 30));        list.add(new Student("刘晓曲", 28));        list.add(new Student("武鑫", 29));        list.add(new Student("林青霞", 27));                int count=Collections.frequency(list, new Student("林青霞", 27));        System.out.println(count);    }}