In this article the following uses of Enum is mentioned:
– Simple enum
– Enums with multiple values
– Convert enums to String, String[], List
– Convert String to enum
– Get enum values
– Overloaded enum constructors
Example 1: Simple enum
This enum contains 3 fil type constants, and a default constuctor (with private access modifier).
public enum SimpleFileType
{
DOCX,
PDF,
XLSX;
}
Example 2: Enum with multiple values
This enum contains 3 file type constants, and each constant has two values (file extension, and mime type) which are passed through the explicit constructor.
These values can be accessed using corresponding get methods (Refer Example 3).
Enum constructor is implicitly private; public or protected access modifiers are not allowed.
public enum FileType
{
DOCX ( “.docx”, “application/vnd.openxmlformats-officedocument.wordprocessingml.document” ),
PDF ( “.pdf”, “application/pdf” ),
XLSX ( “.xlsx”, “application/vnd.openxmlformats-officedocument.spreadsheetml.sheet” );
private final String fileExtension;
private final String mimeType;
FileType( String fileExtension, String mimeType )
{
this.fileExtension = fileExtension;
this.mimeType = mimeType;
}
public String getFileExtension()
{
return fileExtension;
}
public String getMimeType()
{
return mimeType;
}
}
Example 3: Uses of enum
package com.codebonneamie.demo;
import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;
|import java.util.stream.Stream;
class EnumTest
{
public static void main( String args[] )
{
//Get value of an enum constant
System.out.printf( “Get first value: %s %n”, FileType.PDF.getMimeType() );
System.out.printf( “Get second value: %s %n”, FileType.DOCX.getFileExtension() );
//String to enum
FileType fileType = FileType.valueOf( “PDF” );
//Enum to String
String str = FileType.XLSX.toString();
System.out.printf( “Enum to String: %s %n”, str );
//Get enum values
FileType[] fileTypes = FileType.values();
//Enum to List
List<String> list = Stream.of( FileType.values() )
.map( Enum :: name )
.collect( Collectors.toList() );
System.out.println( “Enum to List: ” + list );
//Enum to String[]
String[] arr = Stream.of( FileType.values() )
.map( Enum :: name )
.toArray( String[] :: new );
System.out.println( “Enum to String[]: ” + Arrays.asList( arr ) );
}
}
Output
Get first value: application/pdf
Get second value: .docx
Enum to String: XLSX
Enum to List: [DOCX, PDF, XLSX]
Enum to String[]: [DOCX, PDF, XLSX]
Example 4: Overloaded enum constructors
public enum CurrencyType
{
USA ( “North America” ),
INDIA ( “South Asia”, “INR” ),
UK ( “North-West Europe”, “GBP” ),
ECUADOR( “North-West South America” );
private final String region;
private final String currency;
CurrencyType( String region )
{
this.region = region;
this.currency = “USD”;
}
CurrencyType( String region, String currency )
{
this.region = region;
this.currency = currency;
}
public String getRegion()
{
return region;
}
public String getCurrency()
{
return currency;
}
}