code: static public BooleanExpression AND(BooleanExpression... operands){
  		BooleanExpression result = new BooleanExpression(OPERATOR_AND);
  		result.addOperand(operands);
  		return result;
  	}
docs: 创建用AND连接的表达式
  @param operands
  @return	用AND连接之后的表达式