How to get max value from stream in java8-javaTutorial-php.cn

java8's stream takes max

public static void main(String[] args) { List list = Arrays.asList(1, 2, 3, 4, 5, 6); Integer max = list.stream().max((a, b) -> { if (a > b) { return 1; } else return -1; }).get(); System.out.println(max); }

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Note: The size is judged here through positive and negative numbers and 0 values. Instead of writing it directly as

if (a > b) { return a; } else return b;

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, you can simplify the writing

int max = list.stream().max((a, b) -> a > b ? 1 : -1).get();

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java8 stream detailed explanation~aggregation (max/min/count)

max,You must be familiar with the words minandcount. Yes, we often use them for data statistics in mysql.

These concepts and usages are also introduced in Java stream, which greatly facilitates our data statistics work on collections and arrays.

How to get max value from stream in java8

"Case 1: Get the longest element in the String collection."

public class StreamTest { public static void main(String[] args) { List list = Arrays.asList("adnm", "admmt", "pot", "xbangd", "weoujgsd"); Optional max = list.stream().max(Comparator.comparing(String::length)); System.out.println("最长的字符串：" + max.get()); } }

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"Case 2: Get the maximum value in the Integer collection."

public class StreamTest { public static void main(String[] args) { List list = Arrays.asList(7, 6, 9, 4, 11, 6); // 自然排序 Optional max = list.stream().max(Integer::compareTo); // 自定义排序 Optional max2 = list.stream().max(new Comparator() { @Override public int compare(Integer o1, Integer o2) { return o1.compareTo(o2); } }); System.out.println("自然排序的最大值：" + max.get()); System.out.println("自定义排序的最大值：" + max2.get()); } }

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"Case 3: Get the employee with the highest salary."

public class StreamTest { public static void main(String[] args) { List personList = new ArrayList(); personList.add(new Person("Tom", 8900, 23, "male", "New York")); personList.add(new Person("Jack", 7000, 25, "male", "Washington")); personList.add(new Person("Lily", 7800, 21, "female", "Washington")); personList.add(new Person("Anni", 8200, 24, "female", "New York")); personList.add(new Person("Owen", 9500, 25, "male", "New York")); personList.add(new Person("Alisa", 7900, 26, "female", "New York")); Optional max = personList.stream().max(Comparator.comparingInt(Person::getSalary)); System.out.println("员工工资最大值：" + max.get().getSalary()); } }

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"Case 4: Calculate the number of elements greater than 6 in the Integer set."

import java.util.Arrays; import java.util.List; public class StreamTest { public static void main(String[] args) { List list = Arrays.asList(7, 6, 4, 8, 2, 11, 9); long count = list.stream().filter(x -> x > 6).count(); System.out.println("list中大于6的元素个数：" + count); } }

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