內容簡介

本文主要說明在Java8及以上版本中，使用stream().filter()來過濾一個List對象，查找符合條件的對象集合。

List對象類（StudentInfo）

public class StudentInfo implements Comparable<StudentInfo> {

//名稱
private String name;

//性別 true男 false女
private Boolean gender;

//年齡
private Integer age;

//身高
private Double height;

//出生日期
private LocalDate birthday;

public StudentInfo(String name, Boolean gender, Integer age, Double height, LocalDate birthday){
this.name = name;
this.gender = gender;
this.age = age;
this.height = height;
this.birthday = birthday;
}

public String toString(){
String info = String.format("%s\t\t%s\t\t%s\t\t\t%s\t\t%s",this.name,this.gender.toString(),this.age.toString(),this.height.toString(),birthday.toString());
return info;
}

public static void printStudents(List<StudentInfo> studentInfos){
System.out.println("[姓名]\t\t[性別]\t\t[年齡]\t\t[身高]\t\t[生日]");
System.out.println("----------------------------------------------------------");
studentInfos.forEach(s->System.out.println(s.toString()));
System.out.println(" ");
}

@Override
public int compareTo(StudentInfo ob) {
return this.age.compareTo(ob.getAge());
//return 1;
}

public String getName() {
return name;
}

public void setName(String name) {
this.name = name;
}

public Boolean getGender() {
return gender;
}

public void setGender(Boolean gender) {
this.gender = gender;
}

public Integer getAge() {
return age;
}

public void setAge(Integer age) {
this.age = age;
}

public Double getHeight() {
return height;
}

public void setHeight(Double height) {
this.height = height;
}

public LocalDate getBirthday() {
return birthday;
}

public void setBirthday(LocalDate birthday) {
this.birthday = birthday;
}
}

StudentInfo對象類

測試數據

//測試數據，請不要糾結數據的嚴謹性
List<StudentInfo> studentList = new ArrayList<>();
studentList.add(new StudentInfo("李小明",true,18,1.76,LocalDate.of(2001,3,23)));
studentList.add(new StudentInfo("張小麗",false,18,1.61,LocalDate.of(2001,6,3)));
studentList.add(new StudentInfo("王大朋",true,19,1.82,LocalDate.of(2000,3,11)));
studentList.add(new StudentInfo("陳小跑",false,17,1.67,LocalDate.of(2002,10,18)));

輸出Students列表

 //輸出List
StudentInfo.printStudents(studentList);

輸出結果如下圖：

 使用filter()過濾List

//查找身高在1.8米及以上的男生
List<StudentInfo> boys = studentList.stream().filter(s->s.getGender() && s.getHeight() >= 1.8).collect(Collectors.toList());
//輸出查找結果
StudentInfo.printStudents(boys);

結果如下圖：