java查找元素计算个数,Java Stream - 如何计数元素...
import java.util.Arrays;
import java.util.List;
import java.util.stream.Stream;
public class Main{
public static void main(String[] argv){
List persons = Arrays.asList(new Person("Joe", 12), new Person("Jim", 34), new Person("John", 23));
Stream personsOver18 = persons.stream().filter(p -> p.getAge() > 18);
personsOver18.forEach(p -> System.out.println(p.getFirstName()));
}
}
class Person {
private String firstName;
private String lastName;
private int age;
public Person(String firstName) {
this.firstName = firstName;
}
public Person(String firstName, int age) {
this.firstName = firstName;
this.age = age;
}
public String getFirstName() {
return firstName;
}
public void setFirstName(String firstName) {
this.firstName = firstName;
}
public String getLastName() {
return lastName;
}
public void setLastName(String lastName) {
this.lastName = lastName;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
@Override
public String toString() {
return "Person [firstName=" + firstName + ", lastName=" + lastName
+ ", age=" + age + "]";
}
}
import java.util.Arrays; import java.util.List; import java.util.stream.Stream; public class Main{ public static void main(String[] argv){ List persons = Arrays.asList(new Person("Joe", 12), new Person("Jim", 34), new Person("John", 23)); Stream personsOver18 = persons.stream().filter(p -> p.getAge() > 18); personsOver18.forEach(p -> System.out.println(p.getFirstName())); } } class Person { private String firstName; private String lastName; private int age; public Person(String firstName) { this.firstName = firstName; } public Person(String firstName, int age) { this.firstName = firstName; this.age = age; } public String getFirstName() { return firstName; } public void setFirstName(String firstName) { this.firstName = firstName; } public String getLastName() { return lastName; } public void setLastName(String lastName) { this.lastName = lastName; } public int getAge() { return age; } public void setAge(int age) { this.age = age; } @Override public String toString() { return "Person [firstName=" + firstName + ", lastName=" + lastName + ", age=" + age + "]"; } }