Java8 Stream 基本操作示例

朱雀 2022-06-13 12:07 228阅读 0赞

package Stream;
    
    import java.util.ArrayList;
    import java.util.Arrays;
    import java.util.IntSummaryStatistics;
    import java.util.List;
    import java.util.Optional;
    import java.util.OptionalInt;
    import java.util.stream.Collectors;
    
    public class Java8Stream { 
        public static void main(String[] args) {
            System.out.println("hello Stream");
            List<Person> list=getPersoms();
    
            //调用Stream(流)API函数
            //List<Person> studentList
            boolean isAllMatch=list.stream().allMatch(Person::isStudent);
            boolean isAnyMatch=list.stream().anyMatch(Person::isStudent);
            boolean isALLNotMatch=list.stream().noneMatch(Person::isStudent);
            System.out.println("is All student? "+isAllMatch);
            System.out.println("is Any student? "+isAnyMatch);
            System.out.println("is no student? "+isALLNotMatch);
    
            List<String> studentList=list.stream().
                    filter(Person::isStudent).//筛选出学生
                    //map((Person person)->person.getName()).//获取学生名字形成新的流 map(Person::getName). collect(Collectors.toList());//将新的流返回给studentList System.out.println("studentList: "+studentList); //flatMap List<String> strlist=new ArrayList<String>(); strlist.add("I am a boy"); strlist.add("I love the girl"); strlist.add("But the girl loves another girl"); List<String> resultlist=strlist.stream(). map(line->line.split(" ")).//转化为String[] flatMap(Arrays::stream).//转化为Stream distinct().//去除重复的String collect(Collectors.toList());//返回集合 System.out.println("resultlist: "+resultlist); //获取第一个元素findFirst Optional<Person> person = list.stream().findFirst(); System.out.println("findFirst: "+person.get()); OptionalInt maxAge =list.stream().mapToInt(Person::getAge).max(); System.out.println("maxAge: "+maxAge.getAsInt()); IntSummaryStatistics all=list.stream().collect(Collectors.summarizingInt(Person::getAge)); System.out.println("sumAge:"+all.getSum()+" aver"+all.getAverage() +" minAge"+all.getMin()+" maxAge"+all.getMax()); } /** * 测试数据 * @return */ public static List<Person> getPersoms(){ List<Person> list=new ArrayList<Person>(); Person person; for(int i=0;i<10;i++){ person=new Person(); person.setAge(i); person.setName("lice"+String.valueOf(i)); person.setStudent(true); list.add(person); } return list; } /** * 测试数据 * @return */ public static List<Integer> getNumbers(){ List<Integer> list=new ArrayList<Integer>(); for(int i=0;i<10;i++) list.add(i); return list; } }