JAVA 8 lambda 表达式filter实现按某个属性值查找对象集合中符合条件的对象

-----------------------------核心方法-----------------------

T1是个对象

//当前时间
Date now = new Date();

long nowLong = DateUtil.dateToLong(now);

//当前时间+10分钟
Date dateAdd = DateUtil.dateAdd(now, 600000);

long dateAddLong = DateUtil.dateToLong(dateAdd);



//filter
List collect = t1s.stream()

        .filter(T1 -> (T1.getSlong()) >= nowLong && T1.getSlong() <= dateAddLong)

        .collect(Collectors.toList());

for (int i = 0; i < collect.size(); i++){

    System.out.println("10分钟内测试" + collect.get(i).getS());

}

---------------------以下十个DEMO-----------------------

public static void main(String[] args){

    long i = 1;

    
    List studentList=new ArrayList<>();

    studentList.add(new Student(i++,"三1班","0101","小明","男",10));

    studentList.add(new Student(i++,"三1班","0101","小灰","男",8));

    studentList.add(new Student(i++,"三1班","0101","小龙","男",9));

    studentList.add(new Student(i++,"三1班","0101","小美","女",11));

    studentList.add(new Student(i++,"三1班","0101","小丽","女",10));



    
    System.out.println("最大年龄:"+ studentList.stream().mapToInt(Student::getAge).max().getAsInt());

    System.out.println("最小年龄:"+studentList.stream().mapToInt(Student::getAge).min().getAsInt());

    System.out.println("平均年龄:"+ studentList.stream().mapToDouble(Student::getAge).average().getAsDouble());



    
    List studyScoreList = new ArrayList<>();

    i=1;

    studyScoreList.add(new StudyScore(i++,"语文","小明",new BigDecimal(58.5)));

    studyScoreList.add(new StudyScore(i++,"语文","小灰",new BigDecimal(59.5)));

    studyScoreList.add(new StudyScore(i++,"语文","小龙",new BigDecimal(67)));

    studyScoreList.add(new StudyScore(i++,"语文","小美",new BigDecimal(99)));

    studyScoreList.add(new StudyScore(i++,"语文","小丽",new BigDecimal(98)));

    studyScoreList.add(new StudyScore(i++,"数学","小明",new BigDecimal(30)));

    studyScoreList.add(new StudyScore(i++,"数学","小灰",new BigDecimal(15)));

    studyScoreList.add(new StudyScore(i++,"数学","小龙",new BigDecimal(62)));

    studyScoreList.add(new StudyScore(i++,"数学","小美",new BigDecimal(97)));

    studyScoreList.add(new StudyScore(i++,"数学","小丽",new BigDecimal(97.7)));



    
    List ywStudyScoreList = studyScoreList.stream().filter(m1->"语文".equals(m1.getCourse())).collect(Collectors.toList());

    System.out.println("语文成绩集合：");

    for(StudyScore studyScore:ywStudyScoreList)

    {

        System.out.println("id:"+studyScore.get_id()+" - "+studyScore.getCourse()+" - "+studyScore.getName()+" - "+studyScore.getScore().setScale(2,RoundingMode.HALF_UP));

    }



    
    BigDecimal totalYwStudyScore= ywStudyScoreList.stream().map(StudyScore::getScore).reduce(BigDecimal.ZERO, BigDecimal::add);    //求和
    System.out.println("语文成绩综和:"+totalYwStudyScore);



    
    long personNum=ywStudyScoreList.size();

    System.out.println("语文参考人数:"+personNum);



    
    System.out.println("语文平均分:"+(totalYwStudyScore.divide(new BigDecimal(personNum))).setScale(2, RoundingMode.HALF_UP));

}

    * 学生类
            */

public class Student {

    
    private long studentId;

    
    private String cls;

    
    private String number;

    
    private String name;

    
    private String sex;

    
    private int age;



    public Student(long studentId, String cls, String number, String name, String sex, int age) {

        this.studentId = studentId;

        this.cls = cls;

        this.number = number;

        this.name = name;

        this.sex = sex;

        this.age = age;

    }



    public long getStudentId() {

        return studentId;

    }



    public void setStudentId(long studentId) {

        this.studentId = studentId;

    }



    public String getCls() {

        return cls;

    }



    public void setCls(String cls) {

        this.cls = cls;

    }



    public String getNumber() {

        return number;

    }



    public void setNumber(String number) {

        this.number = number;

    }



    public String getName() {

        return name;

    }



    public void setName(String name) {

        this.name = name;

    }



    public String getSex() {

        return sex;

    }



    public void setSex(String sex) {

        this.sex = sex;

    }



    public int getAge() {

        return age;

    }



    public void setAge(int age) {

        this.age = age;

    }

}






public class StudyScore {

    
    private long _id;

    
    private String course;

    
    private String name;

    
    private BigDecimal score;



    public StudyScore(long _id, String course, String name, BigDecimal score) {

        this._id = _id;

        this.course = course;

        this.name = name;

        this.score = score;

    }



    public long get_id() {

        return _id;

    }



    public void set_id(long _id) {

        this._id = _id;

    }



    public String getCourse() {

        return course;

    }



    public void setCourse(String course) {

        this.course = course;

    }



    public String getName() {

        return name;

    }



    public void setName(String name) {

        this.name = name;

    }



    public BigDecimal getScore() {

        return score;

    }



    public void setScore(BigDecimal score) {

        this.score = score;

    }

}