CODEWITHSUNDEEP
javaswitch-statement
Jean Tennie
Jean Tennie

Reputation: 253

Switch in elegant way in java 1.6 for string

I'm using java 1.6 and i know that from java 1.7 there is option to switch on string but here i use the if/elseif to route type name,my question if there is a elegant way that i can change it to switch Yet

public static SwitchType<?> switchT(final String typeName,
                                    final String memberName) {

    if (typeName.equals("java.lang.String")) {
        return new SwitchInputType<String>(new String(memberName + " "));

    } else if (typeName.equals("char")) {
        return new SwitchInputType<Character>(new Character('a'));

    } else if (typeName.equals("decimal") || 
               typeName.equals("java.math.BigDecimal")) {
        return new SwitchInputType<BigDecimal>(new BigDecimal("34.58"));

    } else if (typeName.equals("boolean")) {

    }

Upvotes: 1

Views: 7002

Answers (3)

Blank Chisui
Blank Chisui

Reputation: 1073

Although it might be a little counter intuitive using enum has proven quite powerful in that regard.

Every enum has a valueOf(String) method that returns an Element for that name. Then you may use the retrieved Element in a switch statement. The only ugly part is that valueOf(String) throws an IllegalArgumentException. So catching that is equivalent to a default case.

enum Type{
    JAVA_LANG_STRING;
    CHAR;
    DECIMAL;
    BOOLEAN;
    JAVA_LANG_BIGDECIMAL;
}

public static SwitchType<?> switchT(final String typeName,
                                final String memberName) {

    try{
    Type t = Type.valueOf(typeName.toUppercase().replace(".","_"));
    switch(t){
    case Type.JAVA_LANG_STRING: return new SwitchInputType<String>(new String(memberName + " "));
    case Type.CHAR: return new SwitchInputType<Character>(new Character('a'));
    case Type.DECIMAL:
    case Type.JAVA_MATH_BIGDECIMAL: return new SwitchInputType<BigDecimal>(new BigDecimal("34.58"));
    }catch(IllegalArgumentException e){
        //default case
    }
}

Also enums may implement interfaces. Either by providing one implementation for each element or one global one.

interface SwitchInputTypeFacotry {

    SwitchInputType get(String arg);

}
enum TypeName implements SwitchInputTypeFacotry{
    CHAR{
        SwitchInputType get(String arg){
            return new SwitchInputType<Character>(new Character('a'));
        }
    }
    [...]
}

public static SwitchType<?> switchT(final String typeName,
                                final String memberName) {

    try{
        SwitchInputTypeFacotry t = Type.valueOf(typeName.toUppercase().replace(".","_"));
        return t.get(memberName);
    }catch(IllegalArgumentException e){
        //default case
    }
}

The second way makes it very easy to extend functionality (as long as it stays in one module, subclassing is not possible with enums).

Upvotes: 1

JB Nizet
JB Nizet

Reputation: 691675

You could use a Map<String, SwitchTypeFactory>:

public interface SwitchTypeFactory {
   SwitchType<?> create(String memberName);
}

...

private static Map<String, SwitchTypeFactory> factories = new HashMap<String, SwitchTypeFactory>();

static {
   factories.put("java.lang.String", new SwitchTypeFactory() {
        @Override
        public SwitchType<?> create(String memberName) {
            return new SwitchInputType<String>(memberName + " ");
        }
    });

    factories.put("char", new SwitchTypeFactory() {
        @Override
        public SwitchType<?> create(String memberName) {
            return new SwitchInputType<Character>(Character.valueOf('a'))
        }
    });
    ...
}

public static SwitchType<?> switchT(final String typeName, final String memberName) {
    return factories.get(typeName).create(memberName);
}

Upvotes: 1

Denys S&#233;guret
Denys S&#233;guret

Reputation: 382102

Many patterns are available, from the use of an enumeration to the use of a Map<String,Implementation> but none of them will be more concise nor faster that what you have in this precise case. They would only make sense if more code was dependent of this typeName.

Upvotes: 1

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