Java新特性之Stream流

public class People {
private String name;
private int age;
private String address;

public People(String name,int age,String address) {
this.name = name;
this.age = age;
this.address = address;
};

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 String getAddress() {
return address;
}

public void setAddress(String address) {
this.address = address;
}

@Override
public String toString() {
return "People [name=" + name + ", age=" + age + ", address=" + address + "]";
}

}

import java.util.Arrays;
import java.util.Collection;
import java.util.Comparator;
import java.util.Iterator;


public class Test10 {
public static void main(String[] args) {
Collection< People > peoples = Arrays.asList(
new People( "a",1,"aa" ),
new People( "b",2,"bb" ),
new People( "c",3,"cc" ), 
new People( "d",4,"dd" ),
new People( "e",5,"ee" ),
new People( "f",6,"ff" ),
new People( "g",7,"gg" ),
new People( "h",8,"hh" ), 
new People( "i",9,"ii" )
);

System.out.print("\n使用iterator\n");
// 使用iterator
for (Iterator iterator = peoples.iterator(); iterator.hasNext();) {
People people = (People) iterator.next();
System.out.println(people.toString());
}

System.out.print("\n使用lambda\n");
// 使用lambda
peoples.forEach(people -> {
System.out.println(people.toString());
});

System.out.print("\n使用方法引用\n");
// 使用方法引用
peoples.forEach(System.out::println);

System.out.print("\n使用Stream流limit()方法\n");

// Stream提供了 forEach()方法來迭代（Iteration）流中的每個資料
// Stream提供了limit()方法用於獲取指定數量的流。
peoples.stream().limit(8).forEach(s -> {
System.out.println(s.toString());
});

System.out.print("\n使用Stream流map()方法\n");
// Stream提供了map()方法用於對映每個元素到對應的結果
peoples.stream().map(people -> {
if (people.getAge() == 5) {
people.setAge(0);
}
return people;
}).forEach(System.out::println);

System.out.print("\n使用Stream流filter()方法\n");
// Stream提供了filter()方法用於通過設定的條件過濾出元素。
// parallelStream提供了count()方法用於統計符合條件的元素的數量
long a = peoples.parallelStream().filter(people -> {
if (people.getAge() == 0 || people.getName().equals("a")) {
return true;
}
return false;
}).count();
System.out.println("符合條件的總共：" + a);

// Stream提供了sorted()方法用於對元素進行排序
System.out.print("\n使用Stream流sorted()方法\n");
peoples.stream().sorted(Comparator.comparing(People::getAge).reversed()).forEach(System.out::println);
}
}

使用iterator
People [name=a, age=1, address=aa]
People [name=b, age=2, address=bb]
People [name=c, age=3, address=cc]
People [name=d, age=4, address=dd]
People [name=e, age=5, address=ee]
People [name=f, age=6, address=ff]
People [name=g, age=7, address=gg]
People [name=h, age=8, address=hh]
People [name=i, age=9, address=ii]

使用lambda
People [name=a, age=1, address=aa]
People [name=b, age=2, address=bb]
People [name=c, age=3, address=cc]
People [name=d, age=4, address=dd]
People [name=e, age=5, address=ee]
People [name=f, age=6, address=ff]
People [name=g, age=7, address=gg]
People [name=h, age=8, address=hh]
People [name=i, age=9, address=ii]

使用方法引用
People [name=a, age=1, address=aa]
People [name=b, age=2, address=bb]
People [name=c, age=3, address=cc]
People [name=d, age=4, address=dd]
People [name=e, age=5, address=ee]
People [name=f, age=6, address=ff]
People [name=g, age=7, address=gg]
People [name=h, age=8, address=hh]
People [name=i, age=9, address=ii]

使用Stream流limit()方法
People [name=a, age=1, address=aa]
People [name=b, age=2, address=bb]
People [name=c, age=3, address=cc]
People [name=d, age=4, address=dd]
People [name=e, age=5, address=ee]
People [name=f, age=6, address=ff]
People [name=g, age=7, address=gg]
People [name=h, age=8, address=hh]

使用Stream流map()方法
People [name=a, age=1, address=aa]
People [name=b, age=2, address=bb]
People [name=c, age=3, address=cc]
People [name=d, age=4, address=dd]
People [name=e, age=0, address=ee]
People [name=f, age=6, address=ff]
People [name=g, age=7, address=gg]
People [name=h, age=8, address=hh]
People [name=i, age=9, address=ii]

使用Stream流filter()方法
符合條件的總共：2

使用Stream流sorted()方法
People [name=i, age=9, address=ii]
People [name=h, age=8, address=hh]
People [name=g, age=7, address=gg]
People [name=f, age=6, address=ff]
People [name=d, age=4, address=dd]
People [name=c, age=3, address=cc]
People [name=b, age=2, address=bb]
People [name=a, age=1, address=aa]
People [name=e, age=0, address=ee]

Java 8 新特性