Java Stream min() and max()
May 21, 2020
Stream.min and Stream.max examples. The java.util.stream.Stream has been introduced in Java 8. Using Stream.min method we get the minimum element of this stream for the given comparator. Using Stream.max method we get the maximum element of this stream for the given comparator. The min and max method both are stream terminal operations.
Let us discuss
min and max methods with examples.
Contents
1. Stream.min()
It returns the minimum element of this stream according to the providedComparator. It is the special case of reduction, for example using Stream.reduce method.
Find the
min method declaration from Java doc.
Optional<T> min(Comparator<? super T> comparator)
Returns: The method returns
Optional containing minimum element or empty.
Throws: The method throws
NullPointerException if minimum element is null.
2. Stream.max()
It returns the maximum element of this stream according to the providedComparator. It is the special case of reduction, for example using Stream.reduce method.
Find the
max method declaration from Java doc.
Optional<T> max(Comparator<? super T> comparator)
Returns: The method returns
Optional containing maximum element or empty.
Throws: The method throws
NullPointerException if maximum element is null.
3. Min and Max for String and Integer
Find the example ofmin and max for the stream of string and integer.
MinMaxDemo1.java
package com.concretepage;
import java.util.Arrays;
import java.util.Comparator;
import java.util.List;
import java.util.Optional;
public class MinMaxDemo1 {
public static void main(String[] args) {
System.out.println("---Min and Max for Integer---");
List<Integer> numList = Arrays.asList(42, 44, 43, 41);
Comparator<Integer> comparator = Comparator.comparing(Integer::intValue);
Optional<Integer> minOptional = numList.stream().min(comparator);
minOptional.ifPresent(e -> System.out.println("Min: " + e));
Optional<Integer> maxOptional = numList.stream().max(comparator);
maxOptional.ifPresent(e -> System.out.println("Max: " + e));
System.out.println("---Min and Max for String---");
List<String> list = Arrays.asList("Mohit", "Nilesh", "Shankar", "Brajesh");
list.stream().min(Comparator.comparing(String::valueOf))
.ifPresent(e -> System.out.println("Min: " + e));
list.stream().max(Comparator.comparing(String::valueOf))
.ifPresent(e -> System.out.println("Max: " + e));
}
}
---Min and Max for Integer--- Min: 41 Max: 44 ---Min and Max for String--- Min: Brajesh Max: Shankar
min and max is the special case of stream reduction. Let us achieve the same using Stream.reduce method.
MinMaxDemoWithReduce.java
package com.concretepage;
import java.util.Arrays;
import java.util.List;
public class MinMaxDemoWithReduce {
public static void main(String[] args) {
System.out.println("---Min and Max for Integer---");
List<Integer> numList = Arrays.asList(42, 44, 43, 41);
//For min
numList.stream().reduce(Integer::min).ifPresent(s -> System.out.println(s)); //41
//For max
numList.stream().reduce(Integer::max).ifPresent(s -> System.out.println(s)); //44
System.out.println("---Min and Max for String---");
List<String> list = Arrays.asList("Mohit", "Nilesh", "Shankar", "Brajesh");
//For min
list.stream().reduce((s1, s2) -> {
if (s1.compareTo(s2) <= 0) {
return s1;
}
return s2;
}).ifPresent(s -> System.out.println(s)); //Brajesh
//For max
list.stream().reduce((s1, s2) -> {
if (s1.compareTo(s2) >= 0) {
return s1;
}
return s2;
}).ifPresent(s -> System.out.println(s)); //Shankar
}
}
4. Min and Max for Object
Find the example ofmin and max for the stream of object.
MinMaxDemo2.java
package com.concretepage;
import java.util.Arrays;
import java.util.Comparator;
import java.util.List;
public class MinMaxDemo2 {
public static void main(String[] args) {
List<User> users = Arrays.asList(
new User("Mahesh", 30),
new User("Krishna", 29),
new User("Virat", 28)
);
System.out.println("---Min and Max on the basis of user name---");
users.stream()
.min(Comparator.comparing(u -> u.getUserName()))
.ifPresent(e -> System.out.println("Min: " + e.getUserName()));
users.stream()
.max(Comparator.comparing(u -> u.getUserName()))
.ifPresent(e -> System.out.println("Max: " + e.getUserName()));
System.out.println("---Min and Max on the basis of age---");
users.stream()
.min(Comparator.comparing(User::getAge))
.ifPresent(e -> System.out.println("Min: " + e.getUserName()));
users.stream()
.max(Comparator.comparing(User::getAge))
.ifPresent(e -> System.out.println("Max: " + e.getUserName()));
}
}
class User {
private String userName;
private int age;
public User(String userName, int age) {
this.userName = userName;
this.age = age;
}
//Sets and Gets
}
---Min and Max on the basis of user name--- Min: Krishna Max: Virat ---Min and Max on the basis of age--- Min: Virat Max: Mahesh
5. Min and Max for Date
Find the example ofmin and max for the stream of date.
MinMaxDemo3.java
package com.concretepage;
import java.time.LocalDate;
import java.time.temporal.ChronoUnit;
import java.util.Arrays;
import java.util.Comparator;
import java.util.List;
public class MinMaxDemo3 {
public static void main(String[] args) {
LocalDate ld = LocalDate.parse("2020-05-15");
List<LocalDate> ldList = Arrays.asList(
ld.minus(10, ChronoUnit.DAYS), //2020-05-05
ld, //2020-05-15
ld.plus(15, ChronoUnit.DAYS) //2020-05-30
);
ldList.stream()
.min(Comparator.comparing(LocalDate::toEpochDay))
.ifPresent(e -> System.out.println("Min: " + e));
ldList.stream()
.max(Comparator.comparing(LocalDate::toEpochDay))
.ifPresent(e -> System.out.println("Max: " + e));
}
}
Min: 2020-05-05 Max: 2020-05-30
6. Using IntStream, LongStream and DoubleStream
Find the Java doc formin and max methods of IntStream, LongStream and DoubleStream.
For
IntStream.
OptionalInt min() OptionalInt max()
LongStream.
OptionalLong min() OptionalLong max()
DoubleStream.
OptionalDouble min() OptionalDouble max()
MinMaxDemo4.java
package com.concretepage;
import java.util.stream.DoubleStream;
import java.util.stream.IntStream;
import java.util.stream.LongStream;
public class MinMaxDemo4 {
public static void main(String[] args) {
System.out.println("--- Min and Max for IntStream ---");
IntStream.of(12, 20, 35, 48).min()
.ifPresent(i -> System.out.println(i));
IntStream.of(12, 20, 35, 48).max()
.ifPresent(i -> System.out.println(i));
System.out.println("--- Min and Max for LongStream ---");
LongStream.of(200, 300, 400).min()
.ifPresent(l -> System.out.println(l));
LongStream.of(200, 300, 400).max()
.ifPresent(l -> System.out.println(l));
System.out.println("--- Min and Max for DoubleStream ---");
DoubleStream.of(110.54, 230.57, 360.65).min()
.ifPresent(l -> System.out.println(l));
DoubleStream.of(110.54, 230.57, 360.65).max()
.ifPresent(l -> System.out.println(l));
}
}
--- Min and Max for IntStream --- 12 48 --- Min and Max for LongStream --- 200 400 --- Min and Max for DoubleStream --- 110.54 360.65
