Collectors minBy() and maxBy() method in Java

This post will discuss Collectors minBy() and maxBy() methods in Java.

The Collectors.maxBy() method returns a Collector that produces the maximal object according to the specified Comparator. Similarly, the Collectors.maxBy() method returns a Collector that produces the minimal object according to the specified Comparator.

We can use it to find the maximum or minimum object in a stream.

import java.util.Arrays;

import java.util.Comparator;

import java.util.List;

import java.util.stream.Collectors;

// `Payroll` class having `employee` and `income` as private fields

class Payroll

{

private String employee;

private Integer income;

public Payroll(String employee, Integer income)

{

this.employee = employee;

this.income = income;

}

public Integer getIncome() {

return income;

}

// other getters and setters

@Override

public String toString() {

return "[" + employee + ", " + String.valueOf(income) + "]";

}

public static Payroll max(Payroll x, Payroll y) {

return x.getIncome() > y.getIncome() ? x : y;

}

class Main

{

// Program to demonstrate `Collectors.minBy()` and `Collectors.maxBy()`

// methods in Java 8 and above

public static void main(String[] args)

{

Payroll p1 = new Payroll("Employee1", 115000);

Payroll p2 = new Payroll("Employee2", 100000);

Payroll p3 = new Payroll("Employee3", 120000);

List<Payroll> salaries = Arrays.asList(p1, p2, p3);

// get a person with the minimum income

Payroll min = salaries.stream()

.collect(Collectors.minBy(

Comparator.comparingInt(Payroll::getIncome)))

.get();

System.out.println("Employee with minimum Salary " + min);

// get a person with the maximum income

Payroll max = salaries.stream()

.collect(Collectors.maxBy(

Comparator.comparingInt(Payroll::getIncome)))

.get();

System.out.println("Employee with maximum Salary " + max);

}

Download Run Code

Output:

Employee with minimum Salary [Employee2, 100000]
Employee with maximum Salary [Employee3, 120000]

We can also pass a lambda function as a comparator, as shown below:

// get a person with the minimum income

Payroll min = salaries.stream()

.collect(Collectors.minBy((x, y) -> x.getIncome() - y.getIncome()))

.get();

// get a person with the maximum income

Payroll max = salaries.stream()

.collect(Collectors.maxBy((x, y) -> x.getIncome() - y.getIncome()))

.get();

Download Run Code

That’s all about the Collectors class minBy() and maxBy() method in Java.

Collectors minBy() and maxBy() method in Java

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