java 8 lambda表达式常用方法及使用场景

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public class People {
    
    private Integer id;

    /**
     * 姓名
     */
    private String name;

    /**
     * 性别
     */
    private Integer sex;

    /**
     * 所属省份
     */
    private String province;

    /**
     * 存款
     */
    private Integer money;

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Integer getMoney() {
        return money;
    }

    public void setMoney(Integer money) {
        this.money = money;
    }

    public String getProvince() {
        return province;
    }

    public void setProvince(String province) {
        this.province = province;
    }

    public Integer getSex() {
        return sex;
    }

    public void setSex(Integer sex) {
        this.sex = sex;
    }

    @Override
    public String toString() {
        return "People{" +
                "id=" + id +
                ", name='" + name + ''' +
                ", sex=" + sex +
                ", province='" + province + ''' +
                ", money=" + money +
                '}';
    }
}

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   peopleArrayList.forEach(item -> {
        // doSomething
    });

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List<Integer> peopleIds = peopleArrayList.stream().map(people -> people.getId()).collect(Collectors.toList());

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List<Integer> peopleIds = peopleArrayList.stream().map(people -> people.getId()).distinct().collect(Collectors.toList());

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List<People> peopleList = peopleArrayList.stream().filter(p -> p.getSex() == 0).collect(Collectors.toList());

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peopleArrayList.sort((p1, p2) -> p2.getId().compareTo(p1.getId()));

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Map<Integer, List<People>> peopleMap = peopleArrayList.stream().collect(Collectors.groupingBy(People::getSex));

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Map<String, List<People>> peopleMap = peopleArrayList.stream().collect(Collectors.groupingBy(people -> people.getSex() + "#" + people.getProvince()));

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int sum = peopleArrayList.stream().mapToInt(People::getMoney).sum();

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long sum = peopleArrayList.stream().mapToLong(People::getMoney).sum();

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double sum = peopleArrayList.stream().mapToDouble(People::getMoney).sum();