本文主要是介绍java Stream,对大家解决编程问题具有一定的参考价值,需要的程序猿们随着小编来一起学习吧!
package newfeature;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.Stream;
public class MyStream {
public static void main(String[] args) {
List<String> strings = Arrays.asList("abc", "", "dsf", "ghg", "abc");
List<User> users = new ArrayList<>();
users.add(new User(1, "a"));
users.add(new User(1, "a"));
users.add(new User(1, "a"));
// 中间操作符返回的是stream
// filter
System.out.println(strings.stream()
.filter(str -> str.contains("d"))
.collect(Collectors.toList()));
// distinct
System.out.println(strings.stream()
.distinct()
.collect(Collectors.toList()));
System.out.println(users.stream()
.distinct()
.collect(Collectors.toList()));
// limit
System.out.println(strings.stream()
.limit(2)// 只取前两个
.collect(Collectors.toList()));
// skip
System.out.println(strings.stream()
.skip(2)// 去掉前两个
.collect(Collectors.toList()));
// map
// 对流中所有元素做统一处理
System.out.println(strings.stream()
.map(str -> "haha" + str)
.collect(Collectors.toList()));
// flatmap
// 字符串转为字符流
System.out.println(strings.stream()
.flatMap(str -> getCharacterByString(str))
.collect(Collectors.toList()));
// sorted
System.out.println(strings.stream()
.sorted()
.collect(Collectors.toList()));
// 终止操作符
// anyMath
System.out.println(strings.stream()
.anyMatch(str->str.contains("a")));
// allMatch
System.out.println(strings.stream()
.anyMatch(str->str.length()>0));
// noneMatch
System.out.println(strings.stream()
.anyMatch(str->str.length()>100));
// findAny
System.out.println(strings.stream()
.findAny());// 返回Option对象 Optional[abc]
System.out.println(strings.stream()
.findAny().get());
// findFirst
System.out.println(strings.stream()
.findFirst());// 返回Option对象 Optional[abc]
System.out.println(strings.stream()
.findAny().get());
// foreach
strings.stream()
.forEach(System.out::println);
// collect
System.out.println(strings.stream().collect(Collectors.toSet()));
System.out.println(strings.stream().collect(Collectors.toList()));
System.out.println(strings.stream()
.collect(Collectors.toMap(v->v, v->v,(oldvalue, newvalue)->newvalue)));// key value 重复的处理方法
// reduce
// 将流中元素反复结合得到一个结果
System.out.println(strings.stream()
.reduce((acc, item)->{return acc + item;}));
// count
System.out.println(strings.stream()
.count());
}
// 根据字符串获取字符
public static Stream<Character> getCharacterByString(String str) {
List<Character> characterList = new ArrayList<>();
for (Character character : str.toCharArray()) {
characterList.add(character);
}
return characterList.stream();
}
}
class User {
private int id;
private String name;
public User(int id, String name) {
this.id = id;
this.name = name;
}
public User() {
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
@Override
public String toString() {
return "User{" +
"id=" + id +
", name='" + name + '\'' +
'}';
}
}
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