文章目录[隐藏]
一、前言
Java 8中引入了Predicate功能接口。
Java Predicate表示一个参数的谓词。
Predicate是一个布尔值的函数。
Java Predicate是一个功能接口，属于java.util.function包。
Predicate的功能方法是test(T t)。
Predicate的其他方法是test、isEqual、and、or、negate和not。
not方法在Java 11中被引入。
在本文章，我们将提供Predicate的例子及其所有方法。
二、test(T t)
boolean test(T t)
test是Predicate的功能方法。它在给定的参数上评估这个谓词。
例1：
PredicateTestDemo1.java
import java.util.function.Predicate;
public class PredicateTestDemo1 {
public static void main(String[] args) {
// Is username valid
Predicate<String> isUserNameValid = u -> u != null && u.length() > 5 && u.length() < 10;
System.out.println(isUserNameValid.test("Mahesh")); //true
// Is password vali<p style="color:transparent">本文来源gao!daima.com搞$代!码网</p>d
Predicate<String> isPasswordValid = p -> p != null && p.length() > 8 && p.length() < 15;
System.out.println(isPasswordValid.test("Mahesh123")); //true
// Word match
Predicate<String> isWordMatched = s -> s.startsWith("Mr.");
System.out.println(isWordMatched.test("Mr. Mahesh")); //true
//Odd numbers
Predicate<Integer> isEven = n -> n % 2 == 0;
for(int i = 0 ; i < 5 ; i++) {
System.out.println("Is "+ i + " even: " + isEven.test(i));
}
}
}
输出结果
true
true
true
Is 0 even: true
Is 1 even: false
Is 2 even: true
Is 3 even: false
Is 4 even: true
例2：
PredicateTestDemo2.java
import java.util.function.Function;
import java.util.function.Predicate;
public class PredicateTestDemo2 {
public static void main(String[] args){
Predicate<Student> maleStudent = s-> s.getAge() >= 20 && "male".equals(s.getGender());
Predicate<Student> femaleStudent = s-> s.getAge() > 18 && "female".equals(s.getGender());
Function<Student,String> maleStyle = s-> "Hi, You are male and age "+s.getAge();
Function<Student,String> femaleStyle = s-> "Hi, You are female and age "+ s.getAge();
Student s1 = new Student("Gauri", 20,"female");
if(maleStudent.test(s1)){
System.out.println(s1.customShow(maleStyle));
}else if(femaleStudent.test(s1)){
System.out.println(s1.customShow(femaleStyle));
}
}
Student.java
import java.util.function.Function;
public class Student {
private String name;
private int age;
private String gender;
private int marks;
public Student(String name, int age, String gender){
this.name = name;
this.age = age;
this.gender = gender;
}
public Student(String name, int age, String gender, int marks){
this.name = name;
this.age = age;
this.gender = gender;
this.marks = marks;
}
public String getName() {
return name;
}
public int getAge() {
return age;
}
public String getGender() {
return gender;
}
public int getMarks() {
return marks;
}
public String customShow(Function<Student,String> fun){
return fun.apply(this);
}
public String toString(){
return name+" - "+ age +" - "+ gender + " - "+ marks;
}
}
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转载请注明原文链接：浅谈Java8新特性Predicate接口
转载请注明原文链接：浅谈Java8新特性Predicate接口
