Lambda表达式：可以方便我们把方法当做参数传递
package airycode_java8.nice1; import org.junit.Test; import java.util.*; /**
* Created by admin on 2018/12/28.
*/
public class TestLambda { public static void main(String[] args) {
List<Employee> employees = filterEmployee(employeeList, new FilterEmployeeByAge());
System.out.println(employees);
System.out.println("-------------------------------------------");
List<Employee> employees2 = filterEmployee(employeeList, new FilterEmployeeBySalary());
System.out.println(employees2); System.out.println("=======================");
test1111();
} //匿名内部类
public void test(){
Comparator<Integer> com = new Comparator<Integer>() {
@Override
public int compare(Integer o1, Integer o2) {
return Integer.compare(o1,o2);
}
}; TreeSet<Integer> ts = new TreeSet<>(com);
} //Lambda表达式
public void testL(){
Comparator<Integer> com = (x,y)->Integer.compare(x,y);
TreeSet<Integer> ts = new TreeSet<>(com);
} //准备数据
static List<Employee> employeeList = Arrays.asList(
new Employee("张三",18,9999.99, Employee.Status.FREE),
new Employee("李四",38,5555.55,Employee.Status.BUSY),
new Employee("王五",50,6666.66,Employee.Status.VOCATION),
new Employee("赵六",16,3333.33,Employee.Status.FREE),
new Employee("田七",8,7777.77,Employee.Status.BUSY)
);
//需求：获取当前公司员工年龄大于35的员工的信息
public List<Employee> filterEmployees(List<Employee>employeeList){
List<Employee> emps = new ArrayList<>(); for (Employee emp:employeeList) {
if (emp.getAge() >= 35) {
emps.add(emp);
}
} return emps;
} //需求：改变1：获取当前公司员工工资大于5000的员工信息
public List<Employee> filterEmployees2(List<Employee>employeeList){
List<Employee> emps = new ArrayList<>(); for (Employee emp:employeeList) {
if (emp.getSalary()>=5000) {
emps.add(emp);
}
} return emps;
} //优化方式1：设计模式优(策略设计模式)化上述需求的改变
public static List<Employee> filterEmployee(List<Employee>employeeList,MyPredicate<Employee> mp){
List<Employee> emps = new ArrayList<>(); for (Employee emp:employeeList) {
if (mp.test(emp)) {
emps.add(emp);
}
} return emps;
} //优化方式2：匿名内部类
public static void test1111(){
List<Employee> list = filterEmployee(employeeList, new MyPredicate<Employee>() {
@Override
public boolean test(Employee employee) {
return employee.getSalary() <= 5000;
}
});
System.out.println(list);
} //优化方式2：匿名内部类
@Test
public void test5(){
List<Employee> list = filterEmployee(employeeList, new MyPredicate<Employee>() {
@Override
public boolean test(Employee employee) {
return employee.getSalary() <= 5000;
}
});
System.out.println(list);
} //优化方式3.Lambda表达式
@Test
public void test6(){
List<Employee> employees = filterEmployee(employeeList, employee -> employee.getSalary() <= 5000);
employees.forEach(System.out::println);
} //优化方式4.上述代码不存在的写法(Stream API)
@Test
public void test7(){
employeeList.stream().filter(employee -> employee.getSalary()<5000).forEach(System.out::println);
System.out.println("----------------------------");
//提取所有的名字
employeeList.stream().map(Employee::getName).forEach(System.out::println);
}
} 新建employee类： package airycode_java8.nice1; /**
* Created by admin on 2018/12/28.
*/
public class Employee { private String name;
private int age;
private double salary; private Status status; public Employee() {
super();
} public Employee(int age){
this.age = age;
} public Employee(String name, int age, double salary, Status status) {
this.name = name;
this.age = age;
this.salary = salary;
this.status = status;
} public Status getStatus() {
return status;
} public void setStatus(Status status) {
this.status = status;
} public String getName() {
return name;
} public void setName(String name) {
this.name = name;
} public int getAge() {
return age;
} public void setAge(int age) {
this.age = age;
} public double getSalary() {
return salary;
} public void setSalary(double salary) {
this.salary = salary;
} @Override
public String toString() {
return "Employee{" +
"name='" + name + '\'' +
", age=" + age +
", salary=" + salary +
", status=" + status +
'}';
} @Override
public boolean equals(Object o) {
if (this == o) return true;
if (o == null || getClass() != o.getClass()) return false; Employee employee = (Employee) o; if (age != employee.age) return false;
if (Double.compare(employee.salary, salary) != 0) return false;
return name != null ? name.equals(employee.name) : employee.name == null;
} @Override
public int hashCode() {
int result;
long temp;
result = name != null ? name.hashCode() : 0;
result = 31 * result + age;
temp = Double.doubleToLongBits(salary);
result = 31 * result + (int) (temp ^ (temp >>> 32));
return result;
} public enum Status{
FREE,BUSY,VOCATION;
}
} package airycode_java8.nice1; /**
* Created by admin on 2018/12/28.
*/
public class FilterEmployeeByAge implements MyPredicate<Employee> { @Override
public boolean test(Employee employee) {
return employee.getAge()>=35;
}
} package airycode_java8.nice1; /**
* Created by admin on 2018/12/28.
*/
public class FilterEmployeeBySalary implements MyPredicate<Employee> { @Override
public boolean test(Employee employee) {
return employee.getSalary()>=5000;
}
} package airycode_java8.nice1; /**
* Created by admin on 2018/12/28.
*/
public interface MyPredicate<T> { public boolean test(T t); }