How to create a list of properties with default values in java?
this code:
import java.util.Properties;
public class P {
public static void main(String[] args) {
Properties defaultProperties=new Properties();
defaultProperties.put("a",1);
System.out.println("default: "+defaultProperties);
Properties properties=new Properties(defaultProperties);
System.out.println("other: "+properties);
}
}
prints:
default: {a=1}
other: {}
using java 8 in eclipse luna.
How do I create a list of properties with default values?
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These are 2 problems with your code.
- The default properties don't work if you use
get()
andput()
.
Instead, you need to execute setProperty()
'getProperty ()' as well.
- When you print a properties file, it will not include properties by default. The method is
toString()
not that optimized.
Use this instead:
Properties defaultProperties=new Properties();
defaultProperties.setProperty("a","s");
System.out.println("default: "+defaultProperties);
Properties properties=new Properties(defaultProperties);
System.out.println("other: "+properties.getProperty("a"));
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You are using defaultProperties.put()
instead defaultProperties.setProperty()
. Therefore your "a" is not recognized as a property.
So use instead:
defaultProperties.setProperty("a", "1");
The object properties
will still print blank (which is what the constructor should do new Properties(Properties defaults)
!), But if you use
System.out.println(properties.getProperty("a"));
You will see that you have received a "1".
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You can use the put () method, but with a String as value: properties.put("a","1");
I know the signature is: Object java.util.Hashtable.put(Object key, Object value)
But with public String getProperty(String key) {
Object oval = super.get(key);
String sval = (oval instanceof String) ? (String)oval : null;
return ((sval == null) && (defaults != null)) ? defaults.getProperty(key) : sval;
}
If the value is not a String, this function returns null.
A end:
Properties properties = new Properties();
properties.put("a" , "1");
System.out.println("default: "+properties);
Properties properties2 = new Properties( properties );
System.out.println("other: "+ properties2.getProperty( "a" ) );
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