logback-android/src/main/java/ch/qos/logback/core/android/SystemPropertiesProxy.java
public String get(String key, String def)
      throws IllegalArgumentException {

    if (SystemProperties == null || getString == null) return null;

    String ret = null;
    try {
      ret = (String) getString.invoke(SystemProperties, new Object[]{ key, def });
    } catch (IllegalArgumentException e) {
      throw e;
    } catch (Exception e) {
    }
    // if return value is null or empty, use the default
    // since neither of those are valid values
    if (ret == null || ret.length() == 0) {
      ret = def;
    }
    return ret;
  }
public String get(String key, String def)
      throws IllegalArgumentException {

    if (SystemProperties == null || getString == null) return null;

    String ret = null;
    try {
      ret = (String) getString.invoke(SystemProperties, new Object[]{ key, def });
    } catch (IllegalArgumentException e) {
      throw e;
    } catch (Exception e) {
    }
    // if return value is null or empty, use the default
    // since neither of those are valid values
    if (ret == null || ret.length() == 0) {
      ret = def;
    }
    return ret;
  }
Get the value for the given key in the Android system properties

@param key
the key to lookup
@param def
a default value to return
@return an empty string if the key isn't found
@throws IllegalArgumentException
if the key exceeds 32 characters