Java 中的 Stream min()方法，示例
原文:https://www . geesforgeks . org/stream-min-method-in-Java-with-examples/
Stream.min() 根据提供的比较器返回流的最小元素。比较器是一个比较函数，它对一些对象集合进行总排序。min()是一个 终端操作 ，结合流元素，返回汇总结果。所以，min()是归约的特例。该方法返回可选实例。
语法:
Optional<T> min(Comparator<? super T> comparator)
Where, Optional is a container object which
may or may not contain a non-null value
and T is the type of objects
that may be compared by this comparator
异常:如果最小元素为空，该方法抛出 空指针异常 。
示例 1 : 整数列表中的最小值。
// Java code for Stream.min() method to get
// the minimum element of the Stream
// according to the provided Comparator.
import java.util.*;
class GFG {
// Driver code
public static void main(String[] args)
{
// Creating a list of integers
List<Integer> list = Arrays.asList(-9, -18, 0, 25, 4);
// Using stream.min() to get minimum
// element according to provided Integer Comparator
Integer var = list.stream().min(Integer::compare).get();
System.out.print(var);
}
}
输出:
-18
例 2 : 使用 min()函数反向比较器获取最大值。
// Java code for Stream.min() method
// to get the minimum element of the
// Stream according to provided comparator.
import java.util.*;
class GFG {
// Driver code
public static void main(String[] args)
{
// Creating a list of integers
List<Integer> list = Arrays.asList(-9, -18, 0, 25, 4);
// Using Stream.min() with reverse
// comparator to get maximum element.
Optional<Integer> var = list.stream()
.min(Comparator.reverseOrder());
// IF var is empty, then output will be Optional.empty
// else value in var is printed.
if(var.isPresent()){
System.out.println(var.get());
}
else{
System.out.println("NULL");
}
}
}
输出:
25
示例 3 : 基于最后一个字符比较字符串。
// Java code for Stream.min() method
// to get the minimum element of the
// Stream according to provided comparator.
import java.util.*;
class GFG {
// Driver code
public static void main(String[] args)
{
// creating an array of strings
String[] array = { "Geeks", "for", "GeeksforGeeks",
"GeeksQuiz" };
// The Comparator compares the strings
// based on their last characters and returns
// the minimum value accordingly.
Optional<String> MIN = Arrays.stream(array).min((str1, str2) ->
Character.compare(str1.charAt(str1.length() - 1),
str2.charAt(str2.length() - 1)));
// If a value is present,
// isPresent() will return true
if (MIN.isPresent())
System.out.println(MIN.get());
else
System.out.println("-1");
}
}
输出:
for
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