Method that returns any type in Java
I'm in a grade 11 computer science course and I'm trying to code a file that simplifies a lot of code. Right now I'm trying to merge input and output into one method;
public static void askln(String text, String type){
System.out.println(text);
if(type.equals("int"))
return getInt();
if(type.equals("char"))
return getChar();
if(type.equals("String"))
return getString();
if(type.equals("double"))
return getDouble();
if(type.equals("float"))
return getFloat();
if(type.equals("long"))
return getLong();
}
getInt() is a method that gets an integer from the user. I'm assuming people will understand what the other getters do.
This code doesn't work because 'void' won't return anything. I was wondering if there was a return type that would allow me to return any value.
java return-type
asked Nov 22 '18 at 18:51
TimTim
92
|
show 1 more comment
I'm in a grade 11 computer science course and I'm trying to code a file that simplifies a lot of code. Right now I'm trying to merge input and output into one method;
public static void askln(String text, String type){
System.out.println(text);
if(type.equals("int"))
return getInt();
if(type.equals("char"))
return getChar();
if(type.equals("String"))
return getString();
if(type.equals("double"))
return getDouble();
if(type.equals("float"))
return getFloat();
if(type.equals("long"))
return getLong();
}
getInt() is a method that gets an integer from the user. I'm assuming people will understand what the other getters do.
This code doesn't work because 'void' won't return anything. I was wondering if there was a return type that would allow me to return any value.
java return-type
asked Nov 22 '18 at 18:51
TimTim
92
3
public static Object?
– Boris the Spider
Nov 22 '18 at 18:52
1
How do I compare strings in Java?
– luk2302
Nov 22 '18 at 18:53
1
Don't compare strings like this. In general, useequals; but in this case, use a switch.
– Andy Turner
Nov 22 '18 at 18:53
1
I think you might do this with generics. Java is much stronger typed than other languages because having an unknown return type leads to bugs. Such a thing is frowned upon.
– K.Nicholas
Nov 22 '18 at 18:53
yeah perhaps make it a class or a struct with all these types and then return struct_name.value or class_object.value as it is hetrogenous (combination of types) hence we use object or struct_name as class identifiers to fetch concrete types
– Himanshu Ahuja
Nov 22 '18 at 18:57
|
show 1 more comment
I'm in a grade 11 computer science course and I'm trying to code a file that simplifies a lot of code. Right now I'm trying to merge input and output into one method;
public static void askln(String text, String type){
System.out.println(text);
if(type.equals("int"))
return getInt();
if(type.equals("char"))
return getChar();
if(type.equals("String"))
return getString();
if(type.equals("double"))
return getDouble();
if(type.equals("float"))
return getFloat();
if(type.equals("long"))
return getLong();
}
getInt() is a method that gets an integer from the user. I'm assuming people will understand what the other getters do.
This code doesn't work because 'void' won't return anything. I was wondering if there was a return type that would allow me to return any value.
java return-type
asked Nov 22 '18 at 18:51
TimTim
92
I'm in a grade 11 computer science course and I'm trying to code a file that simplifies a lot of code. Right now I'm trying to merge input and output into one method;
public static void askln(String text, String type){
System.out.println(text);
if(type.equals("int"))
return getInt();
if(type.equals("char"))
return getChar();
if(type.equals("String"))
return getString();
if(type.equals("double"))
return getDouble();
if(type.equals("float"))
return getFloat();
if(type.equals("long"))
return getLong();
}
getInt() is a method that gets an integer from the user. I'm assuming people will understand what the other getters do.
This code doesn't work because 'void' won't return anything. I was wondering if there was a return type that would allow me to return any value.
java return-type
java return-type
asked Nov 22 '18 at 18:51
TimTim
92
asked Nov 22 '18 at 18:51
TimTim
92
edited Nov 26 '18 at 18:16
Tim
asked Nov 22 '18 at 18:51
TimTim
92
asked Nov 22 '18 at 18:51
TimTim
92
asked Nov 22 '18 at 18:51
TimTim
92
92
3
public static Object?
– Boris the Spider
Nov 22 '18 at 18:52
1
How do I compare strings in Java?
– luk2302
Nov 22 '18 at 18:53
1
Don't compare strings like this. In general, useequals; but in this case, use a switch.
– Andy Turner
Nov 22 '18 at 18:53
1
I think you might do this with generics. Java is much stronger typed than other languages because having an unknown return type leads to bugs. Such a thing is frowned upon.
– K.Nicholas
Nov 22 '18 at 18:53
yeah perhaps make it a class or a struct with all these types and then return struct_name.value or class_object.value as it is hetrogenous (combination of types) hence we use object or struct_name as class identifiers to fetch concrete types
– Himanshu Ahuja
Nov 22 '18 at 18:57
|
show 1 more comment
3
public static Object?
– Boris the Spider
Nov 22 '18 at 18:52
1
How do I compare strings in Java?
– luk2302
Nov 22 '18 at 18:53
1
Don't compare strings like this. In general, useequals; but in this case, use a switch.
– Andy Turner
Nov 22 '18 at 18:53
1
I think you might do this with generics. Java is much stronger typed than other languages because having an unknown return type leads to bugs. Such a thing is frowned upon.
– K.Nicholas
Nov 22 '18 at 18:53
yeah perhaps make it a class or a struct with all these types and then return struct_name.value or class_object.value as it is hetrogenous (combination of types) hence we use object or struct_name as class identifiers to fetch concrete types
– Himanshu Ahuja
Nov 22 '18 at 18:57
3
3
public static Object?– Boris the Spider
Nov 22 '18 at 18:52
public static Object?– Boris the Spider
Nov 22 '18 at 18:52
1
1
How do I compare strings in Java?
– luk2302
Nov 22 '18 at 18:53
How do I compare strings in Java?
– luk2302
Nov 22 '18 at 18:53
1
1
Don't compare strings like this. In general, use
equals; but in this case, use a switch.– Andy Turner
Nov 22 '18 at 18:53
Don't compare strings like this. In general, use
equals; but in this case, use a switch.– Andy Turner
Nov 22 '18 at 18:53
1
1
I think you might do this with generics. Java is much stronger typed than other languages because having an unknown return type leads to bugs. Such a thing is frowned upon.
– K.Nicholas
Nov 22 '18 at 18:53
I think you might do this with generics. Java is much stronger typed than other languages because having an unknown return type leads to bugs. Such a thing is frowned upon.
– K.Nicholas
Nov 22 '18 at 18:53
yeah perhaps make it a class or a struct with all these types and then return struct_name.value or class_object.value as it is hetrogenous (combination of types) hence we use object or struct_name as class identifiers to fetch concrete types
– Himanshu Ahuja
Nov 22 '18 at 18:57
yeah perhaps make it a class or a struct with all these types and then return struct_name.value or class_object.value as it is hetrogenous (combination of types) hence we use object or struct_name as class identifiers to fetch concrete types
– Himanshu Ahuja
Nov 22 '18 at 18:57
|
show 1 more comment
2 Answers
2
active
oldest
votes
You should swap the parameter String type to Class<T> type and your return type to T. You have to define a generic parameter right before the return value, so the signature will be as follows: public static <T> T askln(String text, Class<T> type).
To make your compiler happy, you probably should have the getXXX() methods return Object and casting it while returning to T.
answered Nov 22 '18 at 18:57
László StahorszkiLászló Stahorszki
351211
Could that used with a primitive type (sayfloat), or only with an object (sayFloat)?
– handras
Nov 22 '18 at 19:16
this does not work with primitive types
– László Stahorszki
Nov 22 '18 at 19:21
add a comment |
Another way would be to have a function as a parameter to the method, this solution is based on that since you get the value from the user the input can be handle as a string and then we need a function that converts a string to the desired type.
public static <R> R askln(String text, Function<String, R> function){
System.out.print(text);
String str = getValue();
return function.apply(str);
}
An example for a double
Function<String, Double> f = (Double::parseDouble);
Double d = askln("Type a number ", f);
and an integer
Function<String, Integer> f2 = (Integer::parseInt);
Integer i = askln("Type an integer", f2);
You can then have different functions defined for converting to each supported type.
answered Nov 22 '18 at 19:45
Joakim DanielsonJoakim Danielson
7,9343724
add a comment |
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2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
You should swap the parameter String type to Class<T> type and your return type to T. You have to define a generic parameter right before the return value, so the signature will be as follows: public static <T> T askln(String text, Class<T> type).
To make your compiler happy, you probably should have the getXXX() methods return Object and casting it while returning to T.
answered Nov 22 '18 at 18:57
László StahorszkiLászló Stahorszki
351211
Could that used with a primitive type (sayfloat), or only with an object (sayFloat)?
– handras
Nov 22 '18 at 19:16
this does not work with primitive types
– László Stahorszki
Nov 22 '18 at 19:21
add a comment |
You should swap the parameter String type to Class<T> type and your return type to T. You have to define a generic parameter right before the return value, so the signature will be as follows: public static <T> T askln(String text, Class<T> type).
To make your compiler happy, you probably should have the getXXX() methods return Object and casting it while returning to T.
answered Nov 22 '18 at 18:57
László StahorszkiLászló Stahorszki
351211
Could that used with a primitive type (sayfloat), or only with an object (sayFloat)?
– handras
Nov 22 '18 at 19:16
this does not work with primitive types
– László Stahorszki
Nov 22 '18 at 19:21
add a comment |
You should swap the parameter String type to Class<T> type and your return type to T. You have to define a generic parameter right before the return value, so the signature will be as follows: public static <T> T askln(String text, Class<T> type).
To make your compiler happy, you probably should have the getXXX() methods return Object and casting it while returning to T.
answered Nov 22 '18 at 18:57
László StahorszkiLászló Stahorszki
351211
You should swap the parameter String type to Class<T> type and your return type to T. You have to define a generic parameter right before the return value, so the signature will be as follows: public static <T> T askln(String text, Class<T> type).
To make your compiler happy, you probably should have the getXXX() methods return Object and casting it while returning to T.
answered Nov 22 '18 at 18:57
László StahorszkiLászló Stahorszki
351211
answered Nov 22 '18 at 18:57
László StahorszkiLászló Stahorszki
351211
answered Nov 22 '18 at 18:57
László StahorszkiLászló Stahorszki
351211
answered Nov 22 '18 at 18:57
László StahorszkiLászló Stahorszki
351211
351211
Could that used with a primitive type (sayfloat), or only with an object (sayFloat)?
– handras
Nov 22 '18 at 19:16
this does not work with primitive types
– László Stahorszki
Nov 22 '18 at 19:21
add a comment |
Could that used with a primitive type (sayfloat), or only with an object (sayFloat)?
– handras
Nov 22 '18 at 19:16
this does not work with primitive types
– László Stahorszki
Nov 22 '18 at 19:21
Could that used with a primitive type (say
float), or only with an object (say Float)?– handras
Nov 22 '18 at 19:16
Could that used with a primitive type (say
float), or only with an object (say Float)?– handras
Nov 22 '18 at 19:16
this does not work with primitive types
– László Stahorszki
Nov 22 '18 at 19:21
this does not work with primitive types
– László Stahorszki
Nov 22 '18 at 19:21
add a comment |
Another way would be to have a function as a parameter to the method, this solution is based on that since you get the value from the user the input can be handle as a string and then we need a function that converts a string to the desired type.
public static <R> R askln(String text, Function<String, R> function){
System.out.print(text);
String str = getValue();
return function.apply(str);
}
An example for a double
Function<String, Double> f = (Double::parseDouble);
Double d = askln("Type a number ", f);
and an integer
Function<String, Integer> f2 = (Integer::parseInt);
Integer i = askln("Type an integer", f2);
You can then have different functions defined for converting to each supported type.
answered Nov 22 '18 at 19:45
Joakim DanielsonJoakim Danielson
7,9343724
add a comment |
Another way would be to have a function as a parameter to the method, this solution is based on that since you get the value from the user the input can be handle as a string and then we need a function that converts a string to the desired type.
public static <R> R askln(String text, Function<String, R> function){
System.out.print(text);
String str = getValue();
return function.apply(str);
}
An example for a double
Function<String, Double> f = (Double::parseDouble);
Double d = askln("Type a number ", f);
and an integer
Function<String, Integer> f2 = (Integer::parseInt);
Integer i = askln("Type an integer", f2);
You can then have different functions defined for converting to each supported type.
answered Nov 22 '18 at 19:45
Joakim DanielsonJoakim Danielson
7,9343724
add a comment |
Another way would be to have a function as a parameter to the method, this solution is based on that since you get the value from the user the input can be handle as a string and then we need a function that converts a string to the desired type.
public static <R> R askln(String text, Function<String, R> function){
System.out.print(text);
String str = getValue();
return function.apply(str);
}
An example for a double
Function<String, Double> f = (Double::parseDouble);
Double d = askln("Type a number ", f);
and an integer
Function<String, Integer> f2 = (Integer::parseInt);
Integer i = askln("Type an integer", f2);
You can then have different functions defined for converting to each supported type.
answered Nov 22 '18 at 19:45
Joakim DanielsonJoakim Danielson
7,9343724
Another way would be to have a function as a parameter to the method, this solution is based on that since you get the value from the user the input can be handle as a string and then we need a function that converts a string to the desired type.
public static <R> R askln(String text, Function<String, R> function){
System.out.print(text);
String str = getValue();
return function.apply(str);
}
An example for a double
Function<String, Double> f = (Double::parseDouble);
Double d = askln("Type a number ", f);
and an integer
Function<String, Integer> f2 = (Integer::parseInt);
Integer i = askln("Type an integer", f2);
You can then have different functions defined for converting to each supported type.
answered Nov 22 '18 at 19:45
Joakim DanielsonJoakim Danielson
7,9343724
answered Nov 22 '18 at 19:45
Joakim DanielsonJoakim Danielson
7,9343724
answered Nov 22 '18 at 19:45
Joakim DanielsonJoakim Danielson
7,9343724
answered Nov 22 '18 at 19:45
Joakim DanielsonJoakim Danielson
7,9343724
7,9343724
add a comment |
add a comment |
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3
public static Object?– Boris the Spider
Nov 22 '18 at 18:52
1
How do I compare strings in Java?
– luk2302
Nov 22 '18 at 18:53
1
Don't compare strings like this. In general, use
equals; but in this case, use a switch.– Andy Turner
Nov 22 '18 at 18:53
1
I think you might do this with generics. Java is much stronger typed than other languages because having an unknown return type leads to bugs. Such a thing is frowned upon.
– K.Nicholas
Nov 22 '18 at 18:53
yeah perhaps make it a class or a struct with all these types and then return struct_name.value or class_object.value as it is hetrogenous (combination of types) hence we use object or struct_name as class identifiers to fetch concrete types
– Himanshu Ahuja
Nov 22 '18 at 18:57