Replace multiple if statement for assigning value in java-CodePudding

Let's say we have a function like this:

public String getFullType(String type) {
    
    String result = "";

    if (type.startsWith("INT")) result = "integer";
    if (type.startsWith("STR")) result = "string";
    if (type.startsWith("DBL")) result = "double";

    // some code

    return result;
}

How can I refactor this triple if statement except for using switch? What would be the 'best' way to do this?

CodePudding user response：

You can use switch as follow:

public String getFullType(String type) {
    // Check if type is enough long to not have an ArrayIndexOutOfBoundException
    switch(type.substr(0, 3)) {
       case "INT": return "integer";
       case "STR": return "string";
       case "DBL": return "double";  
    }    
    return "not found";
}

CodePudding user response：

To me, this looks like a case where you are mapping a discrete set of values to new values. That could be done with a Map. Like,

private static final Map<String, String> typeMap = new HashMap<>();
static {
    typeMap.put("INT", "integer");
    typeMap.put("STR", "string");
    typeMap.put("DBL", "double");
}

public String getFullType(String type) {
    return typeMap.getOrDefault(type.substring(0, 3), "unknown");
}

CodePudding user response：

Here's a solution using enums.

First, a definition of the various enum values:

enum TypeEnum {
    INT("integer"),
    STR("string"),
    DBL("double");

    private final String name;

    TypeEnum(String name) {
        this.name = name;
    }
}

Then a new version of getFullType():

public static String getFullType(String type) {
    return TypeEnum.valueOf(type).name;
}

Here's an example of usage output:

System.out.println(getFullType("INT"));
System.out.println(getFullType("STR"));
System.out.println(getFullType("DBL"));

integer
string
double

As posted above, the code will throw an exception if you ask for something that isn't in the enum, such as: getFullType("abc"). You could do a number of things to handle that, here's one as an example, showing a try/catch added to the getFullType() method:

public static String getFullType(String type) {
    try {
        return TypeEnum.valueOf(type).name;
    } catch (IllegalArgumentException e) {
        return "not found";
    }
}

Then it runs fine with unexpected input:

System.out.println(getFullType("abc"))

not found