null or {name:..., value:...}
160170
public @Nullable Scriptable jsFunction_firstHeader(String name) {
		Header h = req.getFirstHeader(name);
		return h == null ? null : makeJsHeader(Context.getCurrentContext(), h);
	}
65241
@SuppressWarnings("unchecked")
	private <T> T nullFor(DataType dataType)
	{
		switch(dataType)
		{
			case Long: return (T)Long.valueOf(-1);
			default: return null;
		}
	}
244636
public static void notNull(@Nullable Object value, String name) {
        if (value == null) {
            throw new IllegalArgumentException(name + " must not be null!");
        }
    }
287600
public boolean isNull(String name) {
		Object value = this.nameValuePairs.get(name);
		return value == null || value == NULL;
	}
971003
function(name) {
			var val = this.get(name);
			if (typeof val === 'undefined' || val === null || val === '')  {
				return null;
			}

			val = val.split(',').map(utils.trim);
			if (!val.length) {
				return null;
			}
			
			return val;
		}
219062
public void putNull(String key) {
		if (this.compiledStatement != null) {
			compiledStatement.bindNull(compiledStatementBindIndex++);
		} else if (values != null) {
			values.putNull(key);
			return;
		}

		names.add(key);
		// values.putNull(key);
		args.add(null);
		valueType.add(ParamType.NULL);
	}
1200539
function (name) {
            if (name == null || this._params == null) {
                return null;
            }
            for (var i = 0, length = this._params.length; i < length; i++) {
                var elt = this._params[i];
                if (elt.name === name) {
                    return elt.value;
                }
            }
            return null;
        }
289365
function (name, value) {
    if (DOMProperty.isReservedProp(name)) {
      return false;
    }
    if ((name[0] === 'o' || name[0] === 'O') && (name[1] === 'n' || name[1] === 'N')) {
      return false;
    }
    if (value === null) {
      return true;
    }
    switch (typeof value) {
      case 'boolean':
        return DOMProperty.shouldAttributeAcceptBooleanValue(name);
      case 'undefined':
      case 'number':
      case 'string':
      case 'object':
        return true;
      default:
        // function, symbol
        return false;
    }
  }
327248
public VarValueDef getValue( Object name)
    {
    int i = findValue( name);
    return i >= 0? values_.get(i) : null;
    }
817586
protected Object checkUndefined(Object val) {
        if (val instanceof String && ((String) val).equals("undefined")) {
            return null;
        }
        return val;
    }
379000
public static <T> void notNull(final String name, final T value) {
    if (value == null) {
      throw new IllegalArgumentException(name + " can not be null");
    }
  }
118092
private String get(String... values) {
            if (values != null) {
                for (String value : values) {
                    if (!StringUtils.isEmpty(value)) {
                        return value;
                    }
                }
            }
            return null;
        }
289828
function ( value ) {
		var tmp;

		if ( value === null || value === undefined ) {
			return undefined;
		}
		else if ( value === "true" ) {
			return true;
		}
		else if ( value === "false" ) {
			return false;
		}
		else if ( value === "null" ) {
			return null;
		}
		else if ( value === "undefined" ) {
			return undefined;
		}
		else if ( value === "" ) {
			return value;
		}
		else if ( !isNaN( tmp = Number( value ) ) ) {
			return tmp;
		}
		else if ( regex.json_wrap.test( value ) ) {
			return json.decode( value, true ) || value;
		}
		else {
			return value;
		}
	}
654220
private void checkForBlank(String value, String name) {
        if (StringUtils.isBlank(value)) {
            throw new IllegalArgumentException(name + " cannot be empty");
        }
    }
133583
function lookup(name){
  utils.assertType(name, 'string', 'name');
  var node = this.lookup(name.val);
  if (!node) return nodes.null;
  return this.visit(node);
}
205285
public static void dumpNonNull(String name, Object obj, StringPrinter printer) {
		dumpIf(name, obj, Predicates.alwaysTrue(), entry -> entry.getValue() != null, printer);
	}
407835
function(node, name) {
                var value = this.getStyle(node.getType() + "-" + name, node);
                return value !== null ? value : this.getStyle(name, node);
            }