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Java 8 BigDecimal Sum Example

By Arvind Rai, September 22, 2016
On this page we will provide java 8 BigDecimal sum example. We will use lambda expression for summation of List, Map and Array of BigDecimal. Using Stream.reduce() method we reduce the collection of BigDecimal to the summation. In case of collection of entity which consists an attribute of BigDecimal, we can use Stream.map() method to get the stream of BigDecimal instances.


BigDecimal Sum with Lambda Expression

To get sum of BigDecimal instances we do as follows using Lambda Expression.
BigDecimal sum = Arrays.stream(bdArray).reduce(BigDecimal.ZERO, (p, q) -> p.add(q)); 
In the above code we are using
Stream.reduce(BigDecimal identity, BinaryOperator<BigDecimal> accumulator)
Accumulator can also be passed as follows in reduce() method.
BigDecimal sum = list.stream().map(Person::getWeight)
                                .reduce(BigDecimal.ZERO, BigDecimal::add);  
Where add() is the method of BigDecimal class. We can also create custom method for summation. For example we have created addWeight() method in our custom class Utility which is using BigDecimal.add() method.
BigDecimal sum = map.values().stream().reduce(BigDecimal.ZERO, Utility::addWeight);  
Find the Utility class.
Utility.java
package com.concretepage;
import java.math.BigDecimal;
public class Utility {
	public static BigDecimal addWeight(BigDecimal w1, BigDecimal w2) {
		return w1.add(w2);
	}
} 

BigDecimal Sum Using List

BigDecimalSumUsingList.java
package com.concretepage;
import java.math.BigDecimal;
import java.util.Arrays;
import java.util.List;
public class BigDecimalSumUsingList {
	public static void main(String[] args) {
		Person p1 = new Person("AAA", new BigDecimal("45.23"));
		Person p2 = new Person("BBB", new BigDecimal("55.43"));
		Person p3 = new Person("CCC", new BigDecimal("65.21"));
		Person p4 = new Person("DDD", new BigDecimal("35.73"));
		List<Person> list = Arrays.asList(p1, p2, p3, p4);
		BigDecimal sum = list.stream().map(Person::getWeight)
		                     .reduce(BigDecimal.ZERO, BigDecimal::add);
		System.out.println(sum);
		
		sum = list.stream().map(p -> p.getWeight())
                .reduce(BigDecimal.ZERO, (b1, b2) -> b1.add(b2));
		System.out.println(sum);
		
		sum = list.stream().map(Person::getWeight)
                .reduce(BigDecimal.ZERO, Utility::addWeight);
		System.out.println(sum);
		
	}
} 
Person.java
package com.concretepage;
import java.math.BigDecimal;
public class Person {
	private String name;
	private BigDecimal weight;
	public Person(String name, BigDecimal weight) {
		this.name = name;
		this.weight = weight;
	}
	public String getName() {
		return name;
	}
	public BigDecimal getWeight() {
		return weight;
	}
} 
Output
201.60
201.60
201.60 

BigDecimal Sum Using Array

BigDecimalSumUsingArray.java
package com.concretepage;
import java.math.BigDecimal;
import java.util.Arrays;
public class BigDecimalSumUsingArray {
	public static void main(String[] args) {
		BigDecimal b1 = new BigDecimal("45.23");
		BigDecimal b2 = new BigDecimal("55.43");
		BigDecimal b3 = new BigDecimal("65.21");
		BigDecimal b4 = new BigDecimal("35.73");
		BigDecimal[] bdArray = {b1, b2, b3, b4};
		
		BigDecimal sum = Arrays.stream(bdArray).reduce(BigDecimal.ZERO, (p, q) -> p.add(q));
		System.out.println(sum);
		sum = Arrays.stream(bdArray).reduce(BigDecimal.ZERO, BigDecimal::add);
		System.out.println(sum);
		sum = Arrays.stream(bdArray).reduce(BigDecimal.ZERO, Utility::addWeight);
		System.out.println(sum);			
	}
} 
Output
201.60
201.60
201.60 

BigDecimal Sum Using Map

BigDecimalSumUsingMap.java
package com.concretepage;
import java.math.BigDecimal;
import java.util.HashMap;
import java.util.Map;
public class BigDecimalSumUsingMap {
	public static void main(String[] args) {
		Map<Integer, BigDecimal> map = new HashMap<>();
		map.put(1, new BigDecimal("45.23"));
		map.put(2, new BigDecimal("55.43"));
		map.put(3, new BigDecimal("65.21"));
		map.put(4, new BigDecimal("35.73"));
		
		BigDecimal sum = map.values().stream().reduce(BigDecimal.ZERO, (p, q) -> p.add(q));
		System.out.println(sum);
		sum = map.values().stream().reduce(BigDecimal.ZERO, BigDecimal::add);
		System.out.println(sum);
		sum = map.values().stream().reduce(BigDecimal.ZERO, Utility::addWeight);
		System.out.println(sum);			
	}
} 
Output
201.60
201.60
201.60 
POSTED BY
ARVIND RAI
ARVIND RAI
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