Java 8 Function之Predicate

Java 8 Predicate 示例

java.util.function.Predicate是在java 8中引入的functional interface。Predicate用于分配lambda表达式。functional interface是返回布尔值的test(T t)。当我们将对象传递给这个方法时,它将通过分配的lambda表达式来评估对象。

语法介绍:

    public static void main(String[] args) {
        //接收一个泛型参数,比较返回boolean值
        Predicate<String> predicate = (v1) -> {
            //此处别的逻辑处理,做简单的语法介绍就不详细写了。
            return v1.equals("1");
        };
//        Predicate<String> predicates = (v1) -> v1.equals("2"); 直接返回结果可这样写

        System.out.println(predicate.test("1"));//true
        System.out.println(predicate.test("2"));//false
    }

找到以下两个表达式

Predicate<Student> maleStudent = s-> s.age >= 20 && "male".equals(s.gender);
Predicate<Student> femaleStudent = s-> s.age > 15 && "female".equals(s.gender);

第一个表达式为男性学生创造了场景,第二个表达式为女学生创造了场景。找到完整的例子

public static void main(String[] args){
      Predicate<Student> maleStudent = s-> s.age >= 20 && "male".equals(s.gender);
      Predicate<Student> femaleStudent = s-> s.age > 15 && "female".equals(s.gender);
      
      Function<Student,String> maleStyle = s-> "Hi, You are male and age "+s.age;
      
      Function<Student,String> femaleStyle = s-> "Hi, You are female and age "+ s.age;
      
      Student s1 = new Student(21,"male");
      if(maleStudent.test(s1)){
          System.out.println(s1.customShow(maleStyle));
      }else if(femaleStudent.test(s1)){
          System.out.println(s1.customShow(femaleStyle));
      }      
  } 

在这个例子中,我们创建了两个Predicate,然后创建一个学生对象,我们将它传递给Predicate的测试方法。 

public class Student {
    public int age;
    public String gender;
    public Student(int age,String gender){
        this.age = age;
        this.gender = gender;
    }
    public  String customShow(Function<Student,String> fun){
        return fun.apply(this);
    }

运行示例,输出如下。

Hi, You are male and age 21

    原文作者:最后的miku殿下
    原文地址: https://blog.csdn.net/Hatsune_Miku_/article/details/73556978
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