Java Language Tutorial => Traditional style to Lambda style

Example

Traditional way

interface MathOperation{
    boolean unaryOperation(int num);
}

public class LambdaTry {
    public static void main(String[] args) {
        MathOperation isEven = new MathOperation() {
            @Override
            public boolean unaryOperation(int num) {
                return num%2 == 0;
            }
        };
        
        System.out.println(isEven.unaryOperation(25));
        System.out.println(isEven.unaryOperation(20));
    }
}

Lambda style

Remove class name and functional interface body.

public class LambdaTry {
    public static void main(String[] args) {
        MathOperation isEven = (int num) -> {
            return num%2 == 0;
        };
        
        System.out.println(isEven.unaryOperation(25));
        System.out.println(isEven.unaryOperation(20));
    }
}

Optional type declaration

MathOperation isEven = (num) -> {
    return num%2 == 0;
};

Optional parenthesis around parameter, if it is single parameter

MathOperation isEven = num -> {
    return num%2 == 0;
};

Optional curly braces, if there is only one line in function body
Optional return keyword, if there is only one line in function body

MathOperation isEven = num -> num%2 == 0;

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Java Language Lambda Expressions Traditional style to Lambda style

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