在java lambda表达式中获取不同返回类型的表达式

Question

I am having a map which stores a key as a character and value as an method call. when I get the value from the map the particular method gets invoked.

Map<Character, IntUnaryOperator> commands = new HashMap<>();
commands.put('a', number -> funtion1(number) );
commands.put('b', number -> funtion1(number) );

char cmd = 'a';
IntUnaryOperator result=  commands.get(cmd);

System.out.println(" Return value is "+result.applyAsInt(101));

Where function1 is as follows,

public static int funtion1(int number){
    System.out.println("hello");
    return number;
}

How can I modify the source code to return an string type or any other type?

Answer 1

• IntUnaryOperator will take int and result int
• UnaryOperator<T> will take T and result T ( IntUnaryOperator is UnaryOperator<Integer> )
• Function<T,R> will take T and result R ( UnaryOperator<T> is Function<T,T> )

So you need Function<Integer,String> :

public static void main(String[] args) throws ParseException {
    Map<Character, Function<Integer, String>> commands = new HashMap<>();
    commands.put('a', Guitar::funtion1); // method reference
    commands.put('b', number -> funtion1(number));

    char cmd = 'a';
    Function<Integer, String> result = commands.get(cmd);                 // Function
    System.out.println("Return value is " + result.apply(55));            // 55 bar
    System.out.println("Return value is " + commands.get('b').apply(32)); // 32 bar
}

public static String funtion1(int text) {
    System.out.println("hello");
    return text + " bar";
}

• I also change one in reference method jusr for