Getting max value from an arraylist of objects?

Question

Is there an easy way to get the max value from one field of an object in an arraylist of objects? For example, out of the following object, I was hoping to get the highest value for the Value field.

Example arraylist I want to get the max value for ValuePairs.mValue from.

ArrayList<ValuePairs> ourValues = new ArrayList<>();
outValues.add(new ValuePairs("descr1", 20.00));
outValues.add(new ValuePairs("descr2", 40.00));
outValues.add(new ValuePairs("descr3", 50.00));

Class to create objects stored in arraylist:

public class ValuePairs {

    public String mDescr;
    public double mValue;

    public ValuePairs(String strDescr, double dValue) {
        this.mDescr = strDescr;
        this.mValue = dValue;
    }
}

I'm trying to get the max value for mValue by doing something like (which I know is incorrect):

double dMax = Collections.max(ourValues.dValue);

dMax should be 50.00.

Answer 1

Use a Comparator with Collections.max() to let it know which is greater in comparison.

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Also See

• How to use custom Comparator

Answer 2

With Java 8 you can use stream() together with it's predefined max() function and Comparator.comparing() functionality with lambda expression:

ValuePairs maxValue = values.stream().max(Comparator.comparing(v -> v.getMValue())).get();

Instead of using a lambda expression, you can also use the method reference directly:

ValuePairs maxValue = values.stream().max(Comparator.comparing(ValuePairs::getMValue)).get();