寫在前面

使用Java8或更高版本，使用stream().filter()來過濾一個List物件，查詢符合條件的物件集合。

List物件類

public class StudentInfo {
private  String name;
private  String gender;
private  int age;
private  int height;

    public StudentInfo setName(String mName) {
        name = mName;
        return  this;
    }

    public StudentInfo setGender(String mGender) {
        gender = mGender;
        return  this;
    }

    public StudentInfo setAge(int mAge) {
        age = mAge;
        return  this;
    }

    public StudentInfo setHeight(int mHeight) {
        height = mHeight;
        return  this;
    }

    public String getName() {
        return name;
    }

    public int getAge() {
        return age;
    }

    public String getGender() {
        return gender;
    }

    public int getHeight() {
        return height;
    }

    @Override
    public String toString() {
        return "StudentInfo{" +
                "name='" + name + '\'' +
                ", gender='" + gender + '\'' +
                ", age=" + age +
                ", height=" + height +
                '}';
    }
}
 

如上就是List物件類了。這裡稍微的使用了一點鏈式程式設計。

測試資料

public static void main(String[] args) {
    List<StudentInfo> lsStudentData = new ArrayList<>();
    //資料新增
    for (int i = 0; i < 30; i++) {
        StudentInfo student = new StudentInfo();
        student.setName("GT Name")
                .setAge(i)
                .setGender(i % 2 != 0 ? "Male" : "Female")
                .setHeight(180);
        lsStudentData.add(student);
    }
    //迴圈遍歷資料
    for (StudentInfo studentItem : lsStudentData) {
        System.out.println(studentItem.toString());
    }
}
 

使用filter()過濾List

過濾要求，我們需要尋找年齡大於等於15的年輕人。

List<StudentInfo> lsYoungStudent = lsStudentData.stream().filter(a -> a.getAge() >= 15).collect(Collectors.toList());
for (StudentInfo studentItem : lsYoungStudent) {
    System.out.println(studentItem.toString());
}

進行年齡大於等於15的過濾操作。

StudentInfo{name='GT Name', gender='Female', age=0, height=180}
StudentInfo{name='GT Name', gender='Male', age=1, height=180}
StudentInfo{name='GT Name', gender='Female', age=2, height=180}
StudentInfo{name='GT Name', gender='Male', age=3, height=180}
StudentInfo{name='GT Name', gender='Female', age=4, height=180}
StudentInfo{name='GT Name', gender='Male', age=5, height=180}
StudentInfo{name='GT Name', gender='Female', age=6, height=180}
StudentInfo{name='GT Name', gender='Male', age=7, height=180}
StudentInfo{name='GT Name', gender='Female', age=8, height=180}
StudentInfo{name='GT Name', gender='Male', age=9, height=180}
StudentInfo{name='GT Name', gender='Female', age=10, height=180}
StudentInfo{name='GT Name', gender='Male', age=11, height=180}
StudentInfo{name='GT Name', gender='Female', age=12, height=180}
StudentInfo{name='GT Name', gender='Male', age=13, height=180}
StudentInfo{name='GT Name', gender='Female', age=14, height=180}
StudentInfo{name='GT Name', gender='Male', age=15, height=180}
StudentInfo{name='GT Name', gender='Female', age=16, height=180}
StudentInfo{name='GT Name', gender='Male', age=17, height=180}
StudentInfo{name='GT Name', gender='Female', age=18, height=180}
StudentInfo{name='GT Name', gender='Male', age=19, height=180}
StudentInfo{name='GT Name', gender='Female', age=20, height=180}
StudentInfo{name='GT Name', gender='Male', age=21, height=180}
StudentInfo{name='GT Name', gender='Female', age=22, height=180}
StudentInfo{name='GT Name', gender='Male', age=23, height=180}
StudentInfo{name='GT Name', gender='Female', age=24, height=180}
StudentInfo{name='GT Name', gender='Male', age=25, height=180}
StudentInfo{name='GT Name', gender='Female', age=26, height=180}
StudentInfo{name='GT Name', gender='Male', age=27, height=180}
StudentInfo{name='GT Name', gender='Female', age=28, height=180}
StudentInfo{name='GT Name', gender='Male', age=29, height=180}
過濾後資料+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
StudentInfo{name='GT Name', gender='Male', age=15, height=180}
StudentInfo{name='GT Name', gender='Female', age=16, height=180}
StudentInfo{name='GT Name', gender='Male', age=17, height=180}
StudentInfo{name='GT Name', gender='Female', age=18, height=180}
StudentInfo{name='GT Name', gender='Male', age=19, height=180}
StudentInfo{name='GT Name', gender='Female', age=20, height=180}
StudentInfo{name='GT Name', gender='Male', age=21, height=180}
StudentInfo{name='GT Name', gender='Female', age=22, height=180}
StudentInfo{name='GT Name', gender='Male', age=23, height=180}
StudentInfo{name='GT Name', gender='Female', age=24, height=180}
StudentInfo{name='GT Name', gender='Male', age=25, height=180}
StudentInfo{name='GT Name', gender='Female', age=26, height=180}
StudentInfo{name='GT Name', gender='Male', age=27, height=180}
StudentInfo{name='GT Name', gender='Female', age=28, height=180}
StudentInfo{name='GT Name', gender='Male', age=29, height=180}
 

可以看到我們的過濾條件年齡大於大於15的過濾操作是有效的。