CODEWITHSUNDEEP
java
Reza
Reza

Reputation: 33

Compute average of two double?

I am trying compute average of two double value, but it dose not work truly. I think it is "rounding error" am I right? and how can I fix it?

point.get(0)=1

point.get(1)=4

double Average = (double)(point.get(0) + point.get(1) / 2);

Output:

Average: 3.0

Why?

Upvotes: 0

Views: 2204

Answers (4)

Pushkar
Pushkar

Reputation: 1

Division takes precedence over addition. Hence, 

Average = (double)(1 + 4/2)  = (double) (1+2) = 3.0

You should probably make it more like

Average = (double)((1+4)/2)

Upvotes: 0

Evan Knowles
Evan Knowles

Reputation: 7511

This has to do with the order of operators - the / has a higher precedence than +, so you are actually getting 1 + (4/2) which does equal 3.

Try this instead:

 double Average = (double)((point.get(0) + point.get(1)) / 2);

The extra brackets will correct your issue.

Upvotes: 0

user207421
user207421

Reputation: 310915

double Average = (double)(point.get(0) + point.get(1) / 2)

Operator precedence trouble. Try this:

double Average = (point.get(0) + point.get(1)) / 2.0;

Upvotes: 1

Juned Ahsan
Juned Ahsan

Reputation: 68715

double Average = (double)(point.get(0) + point.get(1) / 2);

is executed as

Average = (double)(1 + 4/2)  = (double) (1+2) = 3.0

Problem

Divison(/) has higher precedence than addition(+)

Fix

You need to add brackets for proper calculation:

double Average = (double)((point.get(0) + point.get(1)) / 2);

should execute as:

Average = (double)((1 + 4)/2)  = (double) (5/2) = 2.5

Upvotes: 7

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