Java学习路线-38：集合工具类Stack栈、Queue队列、Properties、Collections、Stream、MapReduce

AbstractCollection(Collection)
    - AbstractList(List)
        -ArrayList(List, RandomAccess, Cloneable, java.io.Serializable)
        -Vector(List, RandomAccess, Cloneable, java.io.Serializable)
            -Stack

import java.util.Stack;
class Demo {
    public static void main(String[] args) {
        Stack<String> stack = new Stack<>();
        stack.push("Tom");
        stack.push("Jack");
        System.out.println(stack.pop());
        // Jack
    }
}

@Iterable
    @Collection
        @Queue      // 队列
            @Deque  // 双端队列
AbstractCollection(Collection)
    - AbstractList(List)
        -ArrayList(List, RandomAccess, Cloneable, Serializable)
        -Vector(List, RandomAccess, Cloneable, Serializable)
        -AbstractSequentialList
            -LinkedList(List, Deque, Cloneable, Serializable)
    -AbstractQueue(Queue)
        -PriorityQueue(Serializable)

import java.util.LinkedList;
import java.util.Queue;
class Demo {
    public static void main(String[] args) {
        Queue<String> queue = new LinkedList<>();
        queue.offer("Tom");
        queue.offer("Jack");
        System.out.println(queue.poll());
        // Tom
    }
}

import java.util.PriorityQueue;
import java.util.Queue;
class Demo {
    public static void main(String[] args) {
        Queue<String> queue = new PriorityQueue<>();
        queue.offer("Tom");
        queue.offer("Jack");
        System.out.println(queue.poll());
        // Jack
    }
}

Hashtable<Object,Object>
    -Properties

setProperty // 设置属性
getProperty // 获取属性
store       // 保存
load        // 读取

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.Properties;
class Demo {
    public static void main(String[] args) throws IOException {
        Properties properties = new Properties();
        properties.setProperty("name", "小强");
        properties.setProperty("age", "23");
        // 输出，中文会被转换为unicode码
        properties.store(new FileOutputStream(new File("demo/demo.properties")), "注释");
        // 读取文件
        properties.load(new FileInputStream(new File("demo/demo.properties")));
        System.out.println(properties.getProperty("name"));
        // 小强
    }
}

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
class Demo {
    public static void main(String[] args) {
        List<String> list = new ArrayList<>();
        // 多元素添加
        Collections.addAll(list, "Tom", "Jack", "Steve");
        System.out.println(list);
        // [Tom, Jack, Steve]
        // 列表反转
        Collections.reverse(list);
        System.out.println(list);
        // [Steve, Jack, Tom]
        // 排序
        Collections.sort(list);
        // 二分查找
        System.out.println(Collections.binarySearch(list, "Tom"));
        // 2
    }
}

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.stream.Stream;
class Demo {
    public static void main(String[] args) {
        List<String> list = new ArrayList<>();
        Collections.addAll(list, "Tom", "Jack", "Steve");
        Stream<String> stream = list.stream();
        System.out.println(stream.filter(item->item.toUpperCase().contains("J")).count());
        // 1
    }
}

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.Stream;
class Demo {
    public static void main(String[] args) {
        List<String> list = new ArrayList<>();
        Collections.addAll(list, "Tom", "Jack", "Steve");
        Stream<String> stream = list.stream();
        // 符合条件的数据转为列表输出
        List<String> newList = stream.filter(item->
            item.toUpperCase().contains("J")).collect(Collectors.toList());
        System.out.println(newList);
        // [Jack]
    }
}

import java.util.ArrayList;
import java.util.Collections;
import java.util.IntSummaryStatistics;
import java.util.List;
import java.util.stream.Stream;
class Person {
    private String name;
    private int age;
    public Person(String name, int age) {
        this.name = name;
        this.age = age;
    }
    public String getName() {
        return name;
    }
    public int getAge() {
        return age;
    }
}
class Demo {
    public static void main(String[] args) {
        List<Person> list = new ArrayList<>();
        Collections.addAll(list,
                new Person("小赵", 21),
                new Person("小钱", 22),
                new Person("小孙", 23),
                new Person("小李", 24),
                new Person("小周", 25),
                new Person("小吴", 26)
        );
        Stream<Person> stream = list.stream();
        IntSummaryStatistics stat = stream.filter(
                item -> item.getName().contains("小")
        ).mapToInt(
                item -> item.getAge() + 1
        ).summaryStatistics();
        System.out.println(stat.getSum());      // 147
        System.out.println(stat.getCount());    // 6
        System.out.println(stat.getAverage());  // 24.5
    }
}