Java 8 : Stream API 练习

//店铺属性类
public class Property {
String  name;
// 距离，单位:米
Integer distance;
// 销量，月售
Integer sales;
// 价格，这里简单起见就写一个级别代表价格段
Integer priceLevel;
public Property(String name, int distance, int sales, int priceLevel) {
this.name = name;
this.distance = distance;
this.sales = sales;
this.priceLevel = priceLevel;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Integer getDistance() {
return distance;
}
public void setDistance(Integer distance) {
this.distance = distance;
}
public Integer getSales() {
return sales;
}
public void setSales(Integer sales) {
this.sales = sales;
}
public Integer getPriceLevel() {
return priceLevel;
}
public void setPriceLevel(Integer priceLevel) {
this.priceLevel = priceLevel;
}
@Override
public String toString() {
return "Property [name=" + name + ", distance=" + distance + ", sales=" + sales + ", priceLevel=" + priceLevel
+ "]";
}

}

//JAVA8Stream它提供了对集合操作的增强  与I/O不同
public class TestJAVA8Stream {
public static void main(String[] args) {
/*// Stream操作 List排序
System.out.println("=====JAVA8Stream操作============方法1找到距离我最近的店铺");
Property p1 = new Property("木桶饭", 1000, 500, 2);
Property p2 = new Property("黄焖鸡", 2300, 1500, 3);
Property p3 = new Property("麦当劳", 580, 3000, 1);
Property p4 = new Property("肯德基", 6000, 200, 4);
List<Property> properties = Arrays.asList(p1, p2, p3, p4);
String name2 = properties.stream()
.sorted(Comparator.comparingInt(x -> x.distance))
.findFirst()
.get().name;
System.out.println("距离我最近的店铺是:" + name2);*/
/*System.out.println("======传统操作List排序===========方法二找到距离我最近的店铺");
Property p1 = new Property("木桶饭", 1000, 500, 2);
Property p2 = new Property("黄焖鸡", 2300, 1500, 3);
Property p3 = new Property("麦当劳", 580, 3000, 1);
Property p4 = new Property("肯德基", 6000, 200, 4);
List<Property> properties = Arrays.asList(p1, p2, p3, p4);
Collections.sort(properties, (x, y) -> x.distance.compareTo(y.distance));
String name = properties.get(0).name;
System.out.println("距离我最近的店铺是:" + name);*/
System.out.println("=====迭代=======");
Property p1 = new Property("木桶饭", 1000, 500, 2);
Property p2 = new Property("黄焖鸡", 2300, 1500, 3);
Property p3 = new Property("woi麦当劳", 580, 3000, 1);
Property p4 = new Property("肯德基", 6000, 200, 4);
List<Property> properties = Arrays.asList(p1, p2, p3, p4);
int count = 0;//月销量大于1000的店铺个数
for (Property property : properties) {
if(property.sales > 1000){
count++;
}
}
System.out.println("月销量大于1000的店铺个数:"+count);
//使用内部迭代进行计算
long count2 = properties.stream().filter(p -> p.sales > 1000).count();
System.out.println("月销量大于1000的店铺个数:"+count2);
long count3 =properties.stream().filter(p -> p.distance < 1000).count();//筛选出距离我在1000米内的店铺
long count4 =properties.stream().filter(p -> p.name.length() > 5).count();//筛选出名称大于5个字的店铺
Property property = properties.stream().max(Comparator.comparingInt(p -> p.priceLevel)).get();//筛选出价格最低的店铺
//获取距离我最近的2个店铺
List<Property> properties_s = properties.stream()
.sorted(Comparator.comparingInt(x -> x.distance))
.limit(2)
.collect(Collectors.toList());
//获取所有店铺的名称
List<String> names = properties.stream()
.map(p -> p.name)
.collect(Collectors.toList());
//获取每个店铺的价格等级
Map<String, Integer> map = properties.stream()
.collect(Collectors.toMap(Property::getName, Property::getPriceLevel));
//所有价格等级的店铺列表
Map<Integer, List<Property>> priceMap = properties.stream()
.collect(Collectors.groupingBy(Property::getPriceLevel));

}
}